How do you test for an "Optional" function parameter if it's a "Range"(e.g.
Function X (I As Integer, Optional Cell As Range)?

The "IsMissing()" function is only valid for "Variants", and according to
the help-file, one can test for other types of parameters by testing for
their "Default" values (e.g. Function X (I As Integer, Optional S As String =
"xyz"). If "S" isn't specified it will take on the value of "xyz", which can
be tested.

Does anyone know how and what can be assigned as a default to a "Range"
parameter so it's existence can be tested?

Thanks.