String as function to cell in VBA

I have a problem in VBA. I created a script to sum up every monthly sum (lastrow of the table; every third column should be added) to a yearly sum. For that I create a string with the sum function in it. Then I want to paste the string into a cell under the monthly table.

Whenever I press the button

error 1004

pops up. I tried my best to solve it myself, but I couldn't fix it. If I pass the string to a msgbox it works fine and I get the =sum(...) displayed on my screen.

'Defintions
Dim lastCol As Long
Dim lastRow As Long
Dim i As Integer
Dim k As Integer
Dim x As Integer
Dim l As String
Dim Squantitys As String
Dim year As String
Dim startYear As Integer
Dim str As String
startYear = 8

'Get Dimensions of results
lastRow = Sheets("results").Cells(Rows.Count, 1).End(xlUp).Row
lastCol = Sheets("results").Cells(1, Columns.Count).End(xlToLeft).Column

'Get the new table ready
Sheets("results").Cells(lastRow + 7, 1).Value = "year"
Sheets("results").Cells(lastRow + 7, 2).Value = "total Quantitys"

'add total Quantitys
Squantitys = "=sum("

For i = 2 To lastCol Step 36

     If (lastCol - i) >= 36 Then

          For k = i To i + 33 Step 3

               l = Split(Sheets("results").Cells(lastRow, k).Address, "$")(1)

               Squantitys = Squantitys & l & lastRow & ";"

               x = k + 3

          Next

          l = Split(Sheets("results").Cells(lastRow, x).Address, "$")(1)

          Squantitys = Squantitys & l & lastRow & ")"

     Else

          For k = i To lastCol - 3 Step 3

               l = Split(Sheets("results").Cells(lastRow, k).Address, "$")(1)

               Squantitys = Squantitys & l & lastRow & ";"

               x = k + 3

          Next

          l = Split(Sheets("results").Cells(lastRow, x).Address, "$")(1)

          Squantitys = Squantitys & l & lastRow & ")"

     End If



     'output

     year = Sheets("results").Cells(1, i).Value

     Sheets("results").Cells(lastRow + startYear, 1).Value = year

     'MsgBox Squantitys --- this works fine
     Sheets("results").Cells(lastRow + startYear, 2).Value = Squantitys

     'reset for next loop

     startYear = startYear + 1
     Squantitys = "=sum("

Next