update C1

src/module/Common_Functions.bas

@@ -319,3 +319,7 @@ Public Function FormatDateInput(ByVal inputStr As String) As String
         FormatDateInput = inputStr
     End If
 End Function
+
+Function ColNumToLetter(colNum As Long) As String
+    ColNumToLetter = Split(Cells(1, colNum).Address, "$")(1)
+End Function