Checkbox linked to calcs

[MK]

Hi, I'm trying to link a checkbox to do specific calculations.
Assuming that it's possible, I have the following dilemma:
When checkbox is checked, n=n-a, when unchecked, n.

I wrote the following code but it doesn't work
Dim withMobile As CheckBox

If withMobile.Value = True Then

Range("U66").Select
ActiveCell.FormulaR1C1 = "=RC[60]+RC[90]+RC[102]+RC[114]+RC[126]-RC[108]"
Selection.AutoFill Destination:=Range("U66:U99"), Type:=xlFillDefault

Range("V66").Select
ActiveCell.FormulaR1C1 = "=RC[60]+RC[90]+RC[102]+RC[114]+RC[126]-RC[108]"
Selection.AutoFill Destination:=Range("V66:V99"), Type:=xlFillDefault

Range("W66").Select
ActiveCell.FormulaR1C1 = _

"=IF(FISCAL_YTD=""YES"",RC[-2]-RC[-1],IFERROR(RC[-2]-RC[-1],0))-RC[108]"
Selection.AutoFill Destination:=Range("W66:W99"), Type:=xlFillDefault

Range("L66").Select
ActiveCell.FormulaR1C1 = "=RC[60]+RC[90]+RC[102]+RC[114]+RC[126]-RC[108]"
Selection.AutoFill Destination:=Range("L66:L99"), Type:=xlFillDefault

ElseIf withMobile.Value = False Then

Range("U66").Select
ActiveCell.FormulaR1C1 = "=RC[60]+RC[90]+RC[102]+RC[114]+RC[126]"
Selection.AutoFill Destination:=Range("U66:U99"), Type:=xlFillDefault

Range("V66").Select
ActiveCell.FormulaR1C1 = "=RC[60]+RC[90]+RC[102]+RC[114]+RC[126]"
Selection.AutoFill Destination:=Range("V66:V99"), Type:=xlFillDefault

Range("W66").Select
ActiveCell.FormulaR1C1 = _
"=IF(FISCAL_YTD=""YES"",RC[-2]-RC[-1],IFERROR(RC[-2]-RC[-1],0))"
Selection.AutoFill Destination:=Range("W66:W99"), Type:=xlFillDefault

Range("L66").Select
ActiveCell.FormulaR1C1 = "=RC[60]+RC[90]+RC[102]+RC[114]+RC[126]"
Selection.AutoFill Destination:=Range("L66:L99"), Type:=xlFillDefault

End If


End Sub

Could anyone please help?