IsMissing Function

Syntax:
IsMissing(variantvar)
Group: Variable Info
Description:
Return the True if Optional parameter variantvar does not have a defaultvalue and it did not get a value. An Optional parameter may be omitted in the Sub, Function or Property call.
Parameter Description

ariantvar Return True if this variant parameter's argument expression was not specified in the Sub, Function or Property call.

Example:

Sub Main
Opt 'IsMissing(A)=True
Opt "Hi" 'IsMissing(A)=False
Many 'No args
Many 1,"Hello" 'A(0)=1 A(1)=Hello
OptBye '"Bye"
OptBye "No" '"No"
End Sub

Sub Opt(Optional A)
Debug.Print "IsMissing(A)=";IsMissing(A)
End Sub

Sub Many(ParamArray A())
If LBound(A) > UBound(A) Then
Debug.Print "No args"
Else
For I = LBound(A) To UBound(A)
Debug.Print "A(" & I & ")=" & A(I) & " ";
Next I
Debug.Print
End If
End Sub

Sub OptBye(Optional A As String = "Bye")
Debug.Print A
End Sub