I can call SUM(Sheet1:Sheet3!B1) in A1.

But I cannot call mySum(Sheet1:Sheet3!B1).

What type of object is passed for that kind of range?

Why doesn't the following work? The second MsgBox displays Error.

Function mySum(ParamArray x())
MsgBox LBound(x) & " " & UBound(x)
MsgBox TypeName(x(0))
End Function