How do I test if optional arguments are supplied or not?

Question

How do I test if optional arguments are supplied or not? -- in VB6 / VBA

Function func (Optional ByRef arg As Variant = Nothing)

    If arg Is Nothing Then          


        

Answer 1

Most of these refer to the variant type, or test if a value is blank.

However, sometimes you want to check if a range, workbook, worksheet, or other type of object is not passed, without checking things like sheetnames.

In that case:

DesiredRange is Nothing

Returns a boolean. For example:

    If DestinationRange Is Nothing Then
        MsgBox "Need a destination range when importing data"
    Else
        'We're happy
    End If