Moved code from worksheet to module

I had the following code in a sheet and it worked fine. I moved it to a
module and now I get object required errors.

If Target.Address = "$A$3" Then
Range("C4") = Range("A3")
End If

I tried: If Target.Address = Sheets("Sheet").Range("$A$3") Then
but that dowsn't work either. How can I do this?

Thanks,
Phil