XL5: Visual Basic Procedure to Return Active Drive Letters

• Microsoft Excel for Windows, versions 5.0, 5.0c

SUMMARY

In Microsoft Excel version 5.0, you can create a Visual Basic procedure that uses the Microsoft Windows API (application programming interface) Library to return the drive letters of active drives. Below is an example of Visual Basic code you can use to accomplishing this task.

Sample Visual Basic Procedure

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WARNING: The Declare Function statements listed in the following macro are very sensitive. If used incorrectly, these functions may cause a general protection (GP) fault in Windows or cause serious software problems.

'The following Declare Function should be entered on one single line.
Declare Function GetDriveType Lib "KERNEL" _
    (ByVal nDrive As Integer) As Integer

'Declaration of Constants

' The function below returns an array of drive letters that can be
' assigned to a variant variable or used directly.

    Dim DriveNum As Integer
    Dim UsedDriveArray() As Variant
    Dim CurrentDrive As Integer
    Dim DriveCount As Integer
   'Initializes UsedDriveArray to have zero elements
    ReDim UsedDriveArray(0)
   'Initializes counter variable
    DriveCount = 0
   'Loops through all possible drives (0 = A:, 1 = B:, etc.)
    For DriveNum = 0 To 25
   'Returns DRIVE_INVALID if no drive connected to drive letter
        CurrentDrive = GetDriveType(DriveNum)
        If Not CurrentDrive = DRIVE_INVALID Then
   'Adds the drive letter to the array
            UsedDriveArray(DriveCount) = Chr$(DriveNum + 65) + ":"
            DriveCount = DriveCount + 1
   'Allocates one more array element for current active drive
            ReDim Preserve UsedDriveArray(UBound(UsedDriveArray) + 1)
        End If
    Next
    ReDim Preserve UsedDriveArray(UBound(UsedDriveArray) - 1)
   'Returns the array
    UsedDrives = UsedDriveArray

'The following sub will display a message box for each active drive

Sub DriveTest()
    Dim DriveArray As Variant
    DriveArray = UsedDrives()
    For x = LBound(DriveArray) To UBound(DriveArray)
        MsgBox DriveArray(x)
    Next
End Sub