Why not just use the name property of the sheet's codename? For
example, the following sets of code give the same result:

n1 = 0
For Each oSheet In Sheets(Array("A", "C"))
n1 = n1 + oSheet.[A1]
Next oSheet
Debug.Print "n1 = " & n1 & vbCrLf

n2 = 0
For Each oSheet In Sheets(Array(Sheet1.Name, Sheet3.Name))
n2 = n2 + oSheet.[A1]
Next oSheet
Debug.Print "n2 = " & n2 & vbCrLf