ACC: How to Dial a Phone Number in Microsoft Access (1.x/2.0)

• Microsoft Access versions 1.0, 1.1, 2.0

SUMMARY

Advanced: Requires expert coding, interoperability, and multiuser skills.

This article describes a sample user-defined Access Basic function, DialNumber(), that you can use to dial a telephone number from Microsoft Access using your computer's modem. This method uses Microsoft Windows application programming interface (API) function calls.

Although this function will work with Microsoft Access version 2.0, version 2.0 has a new AutoDialer feature that can be used for dialing telephone numbers. For more information about the AutoDialer feature, search for "AutoDialer" using the Microsoft Access 2.0 Help menu.

This article assumes that you are familiar with Access Basic and with creating Microsoft Access applications using the programming tools provided with Microsoft Access. For more information on Access Basic, please refer to the "Introduction to Programming" manual in Microsoft Access version 1.x, or the "Building Applications" manual in version 2.0.

MORE INFORMATION

To dial a phone number in Microsoft Access, you can use Microsoft Windows API calls in the dynamic-link library (DLL) USER.EXE. There are 17 communication API calls available in USER.EXE, but only the following 3 are used to dial a phone number: OpenComm(), CloseComm(), and WriteComm().

The following steps demonstrate how to create and use the DialNumber() function.

NOTE: In the following sample code, an underscore (_) is used as a line- continuation character. Remove the underscore from the end of the line when re-creating this code in Access Basic.

1. Open the sample database NWIND.MDB.

2. Create a new Access Basic module with the following in the Declarations section:

         Option Explicit
   

         ' The number of seconds to wait for the modem to dial before
         ' .. resetting the modem. If the phone hangs up prematurely
         ' .. try increasing this value by small increments.
         Const WAITSECONDS = 4
   

         Declare Function OpenComm Lib "User" (ByVal lpComName$, _
            ByVal wInQueue%, ByVal wOutQueue%) As Integer
         Declare Function CloseComm Lib "User" (ByVal nCid%) As Integer
         Declare Function WriteComm Lib "User" (ByVal nCid%, _
            ByVal lpBuf$, ByVal nSize%) As Integer
   
         Const ID_CANCEL = 2
         Const MB_OKCANCEL = 1
         Const MB_ICONSTOP = 16, MB_ICONINFORMATION = 64
   
   

3. Add the following function to the module:

         ' ***********************************************************
         ' FUNCTION: DialNumber()
         '
         ' PURPOSE: To dial a telephone number using the computer's modem
         '
         ' ARGUMENTS:
         '    PhoneNumber: The telephone number to dial
         '
         '    CommPort: The communications port the modem is connected
         '              to. Typically, modems are found on COM2, however,
         '              they can be configured for any COM port.
         '
         ' EXAMPLE:
         '    Type the following in the Immediate window using a modem
         '    connected to the COM2 port:
         '
         '       ? DialNumber("555-1212", "COM2")
         '
         ' ***********************************************************
         Function DialNumber (PhoneNumber, CommPort As String)
            Dim Msg As String, MsgBoxType As Integer, MsgBoxTitle As String
            Dim ModemCommand As String
            Dim OpenPort As Integer
            Dim RetVal As Integer
            Dim StartTime
            Dim CR As String: CR = Chr$(13)
            Dim LF As String: LF = Chr$(10)
   
            ' Ask the user to pick up the phone.
            Msg = "Please pickup the phone and choose OK to dial " _
               & PhoneNumber
            MsgBoxType = MB_ICONINFORMATION + MB_OKCANCEL
            MsgBoxTitle = "Dial Number"
            If MsgBox(Msg, MsgBoxType, MsgBoxTitle) = ID_CANCEL Then
               Exit Function
            End If
   
            ' Open the communications port.
            OpenPort = OpenComm(CommPort, 1024, 128)
            If OpenPort < 0 Then
               Msg = "Unable to open communication port " & CommPort
               GoTo Err_DialNumber
            End If
   
            ' Send the telephone number to the modem.
            ModemCommand = "ATDT" & PhoneNumber & CR & LF
            If WriteComm(OpenPort, ModemCommand, Len(ModemCommand)) < 0 Then
               Msg = "Unable to dial number " & PhoneNumber
               GoTo Err_DialNumber
            End If
   
            ' Wait WAITSECONDS seconds for the phone to dial.
            StartTime = Timer
            While Timer < StartTime + WAITSECONDS
               DoEvents
            Wend
   
            ' Reset the modem and take it off line.
            ModemCommand = "ATH0" & CR & LF
            RetVal = WriteComm(OpenPort, ModemCommand, Len(ModemCommand))
   
            ' Close the communications port.
            RetVal = CloseComm(OpenPort)
   
            Exit Function
   
         Err_DialNumber:      'This is not an On Error routine.
            Msg = Msg & CR & CR & "Make sure no other devices are using _
               communication port " & CommPort
            MsgBoxType = MB_ICONSTOP
            MsgBoxTitle = "Dial Number Error"
            MsgBox Msg, MsgBoxType, MsgBoxTitle
   
         End Function
   
   

4. Open the Employees form in Design view.

5. Add a command button with the following properties to the form next to the Home Phone field.

         Microsoft Access 1.x:
   

            ControlName: btnDialPhone
            Caption: Dial
            OnPush: =DialNumber([Home Phone], "COM2")
   
         Microsoft Access 2.0:
   
            Name: btnDialPhone
            Caption: Dial
            OnClick: =DialNumber([Home Phone], "COM2")
   
   

6. View the form in Form view. To dial an employee's home phone number, choose the Dial button.

REFERENCES

For an example of this topic in Microsoft Access for Windows 95 version 7.0, please see the following article in the Microsoft Knowledge Base:

    ARTICLE-ID: Q148857
    TITLE:      ACC: How to Dial a Phone Number Using MS Access 95/97