Such questions are answered with a call to the DirectInputDevice8.GetCapabilities method, which returns the data in a DIDEVCAPS type.

The following code example checks whether the mouse is attached and whether it has a third axis (presumably a wheel):

'diMouse is a valid DirectInputDevice object. 
 
Dim WheelAvailable As Boolean
Dim dicaps as DIDEVCAPS
 
Call diDev.GetCapabilities(dicaps)
WheelAvailable = ((dicaps.lFlags And DIDC_ATTACHED) _
        And (dicaps.lAxes > 2))

Another way to check for a certain button or axis is to call DirectInputDevice8.GetObjectInfo for that object. If the call raises the error DIERR_NOTFOUND, the object is not present. The following code determines whether there is a z-axis, even if it is not the third axis:

Dim didoi As DirectInputDeviceObjectInstance
On Error GoTo NOTFOUND
Set didoi = diDev.GetObjectInfo(DIMOFS_Z, DIPH_BYOFFSET)
On Error GoTo 0
.
.
.
NOTFOUND:
If Err.Number = DIERR_NOTFOUND Then
  MsgBox "No z-axis found."
End If