Sum values from one Worksheet in another Worksheet #vba

I am trying to sum values from my original worksheet in specific cells in my newly created worksheet, which has a template to fill out.
When I used macro recorder, it references the worksheet name, which would not be useful as the worksheet name changes depending on which worksheet I am working in when I run the code.
So I tried changing the worksheet name to a variable "XCXX".
The first argument works so I thought everything was okay, however, on the second argument, it keeps trying to open a file, when it should simply go back to XCXX and pull the values.
Is it a problem with my activesheet changing?

Sub AddWorkbooks()

Dim ChangeOrder As Range
Dim XCXX As Worksheet
Dim CoForm As Worksheet

Set XCXX = ActiveSheet
Set CoForm = Worksheets("+CO Form+")
'Set wbNew = Workbooks.Add

CoForm.Copy After:=Sheets(ActiveSheet.Index)

With CoForm
    Range("A6:D6").Select
    ActiveCell.FormulaR1C1 = XCXX.Range("D2").Value
    Range("AD81").Select
    ActiveCell.FormulaR1C1 = "='XCXX'!R[-64]C[-24]+'XCXX'!R[-64]C[-23]"
    
End With

End Sub

>Solution :

This should be close:

Sub AddWorkbooks()

    Dim ChangeOrder As Range
    Dim XCXX As Worksheet, wb As Workbook
    Dim CoForm As Worksheet, CoFormCopy As Worksheet
    
    Set wb = ActiveWorkbook
    Set XCXX = ActiveSheet
    Set CoForm = wb.Worksheets("+CO Form+")
    
    CoForm.Copy After:=XCXX
    Set CoFormCopy = XCXX.Next 'the copy of "+CO Form+"
    
    With CoFormCopy 'assuming you want to work with the copy?
        .Range("A6:D6").Value = XCXX.Range("D2").Value
        .Range("AD81").FormulaR1C1 = _
           Replace("='<nm>'!R[-64]C[-24]+'<nm>'!R[-64]C[-23]", "<nm>", XCXX.Name)
    End With

End Sub

Note when using With you need to use a period to link (eg) Range() with the object used in the With statement, otherwise it defaults to the active sheet.

Also generally there’s no need to select a range to do something with it.