Macro to autofill a IF function based on the column before it

I am working on a macro that designed to reformat data and it is coming along pretty well, but I keep getting the following error

Run-time error '1004':
Application-defined or object-defined error

Here is the code

Sub BeginReformat()
'Piecing together a macro
    ActiveWorkbook.Sheets(1).Sort.SortFields.Clear
    ActiveWorkbook.Sheets(1).Sort.SortFields.Add Key:=Range("R:R" _
        ), SortOn:=xlSortOnValues, Order:=xlAscending, DataOption:=xlSortNormal
    With ActiveWorkbook.Sheets(1).Sort
        .SetRange Range("A:V")
        .Header = xlYes
        .MatchCase = False
        .Orientation = xlTopToBottom
        .SortMethod = xlPinYin
        .Apply
        Range("C:C,E:E,F:F").Select
        Range("F1").Activate
        Selection.Insert Shift:=xlToRight
        Range("C2").Select
        Range("C2").FormulaR1C1 = "=(RC[20]&""-""&RC[-2]&""-""&RC[1])"
        LastRow = ActiveSheet.UsedRange.Rows.Count
        Range("C2").AutoFill Destination:=Range("C2:C" & LastRow)
        Range("F2").Select
        Range("F2").FormulaR1C1 = "=IF(Sheet1!$A$1 RC[-1]>=1,""Yes"",""No"")"
        LastRow = ActiveSheet.UsedRange.Rows.Count
        Range("F2").AutoFill Destination:=Range("F2:F" & LastRow)
    End With
End Sub

The offending line is

Range("F2").FormulaR1C1 = "=IF(Sheet1!$A$1 RC[-1]>=1,""Yes"",""No"")"

I am sure that I calling this wrong but I am unsure as to how I should be calling it