I must admit I thought there would be some way of catching
the click on the cancel button (vbCancel)...

There is; use this subroutine structure as a guideline...

Sub Test()
Dim strInput As String
strInput = InputBox("Some prompt for input")
If Len(strInput) = 0 Then
If StrPtr(strInput) = 0 Then
MsgBox "User clicked Cancel Button"
Else
MsgBox "No text entry, user clicked Enter"
End If
Else
MsgBox "The user inputted this text: " & strInput
End If
' The subroutine code continues here
End Sub

Rick