You mean something like this?
G7 = 23
AC7 =1
Option Explicit
Sub test()
Dim i As Long
Dim oCell As Range
ActiveSheet.Range("G7:AC7").Cells = "###"
i = ActiveSheet.Range("G7:AC7").Cells.Count
For Each oCell In ActiveSheet.Range("G7:AC7").Cells
oCell.Replace What:="###", Replacement:=i
i = i - 1
Next oCell
End Sub
or
G7 = 22
AC7 =0
Option Explicit
Sub test()
Dim i As Long
Dim oCell As Range
ActiveSheet.Range("G7:AC7").Cells = "###"
i = ActiveSheet.Range("G7:AC7").Cells.Count - 1
For Each oCell In ActiveSheet.Range("G7:AC7").Cells
oCell.Replace What:="###", Replacement:=i
i = i - 1
Next oCell
End Sub