VBA Code Issue

[superfb]

Hi, i have a code where i have tried to adjust it to do the following:

1. At the bottom of column B (in this case row 84) to copy this row and insert it above.
2. I have a if Formula =IF(B81="Mar","Jun",IF(B81="Jun","Sep",IF(B81="Sep","Dec",IF(B81="Dec","Mar")))) - but this keeps referring to B81 rather than the one above it. I would like this VBA code to paste the value.
3. Subsequently then delete the row of data from C:R

The code i have is this which isnt working:

Sub AddRowMonthTab6()

Range("C2").Select
With Range("C" & Rows.Count).End(xlUp)
      .Offset(-10, -2).Resize(, 22).Copy
      .Offset(-10, -2).Insert xlDown
       Application.CutCopyMode = False
       .Offset(-10, 0).Select
     ' Intersect(.EntireRow, Range("C:U")).ClearContents
   End With
   
With Range("C" & Rows.Count).End(xlUp)
.Offset(-10, -1).FormulaR1C1 = "=IF(R[-1]C=""Mar"",""Jun"",IF(R[-1]C=""Jun"",""Sep"",IF(R[-1]C=""Sep"",""Dec"",IF(R[-1]C=""Dec"",""Mar""))))"
.Value = .Value
'Intersect(.EntireRow, Range("D:U")).Clear
End With


With Range("C" & Rows.Count).End(xlUp)
Intersect(.EntireRow, Range("D:U")).Clear
 'End With
 
End Sub

The problem is:

1.Formula doesnt paste value
2.The data it deletes is from row 94

Ideally i would like to change the months in the row 87, 91, 93 and 94

e.g, row 91: When updated it should be December