Using VBA, can I pass a blank date to a COM object?

I have a VFP COM DLL that will accept parameters to write to a record. One parameter is a date. I want the date parameter to accept blank dates. How do I pass a blank date or null from a VBA script to this COM object?

Dim Mydate As Date
Dim o As New MyCom.MyCom

'This works but the date accepted in VFP is 12-30-1899.
o.AddContact("Name", Mydate)

'Works.
o.AddContact("Name", #5/1/2007#)

'Does NOT work. Want to pass blank date.
o.AddContact("Name", ##)

Thanks,

Jerry