Here is a function  that seems to do the trick:

Function SumPos(Numbers)
A = Numbers 'convert range to variant array
Nrows = UBound(A, 1)
Ncols = UBound(A, 2)
SumPos = 0
For r = 1 To Nrows
For c = 1 To Ncols
If A(r, c) > 0 Then
SumPos = SumPos + A(r, c)
End If
Next
Next
End Function