slow cell marching

[Anishtain4]

I have a set of cells which I want to check and clearcontent cells that have 0. there is a total of 32 cell and my code is

For i = 0 To flds
  Call CpyNum(Cells(i + jRowS, ColS), Cells(i + 2, srcCol))
'Next

Sub CpyNum(src As Range, des As Range)
If src <> 0 Then
    des = src
Else
    des.ClearContents
End If
End Sub

but when I run the main sub it is sooo slow. How can you make it faster?