Formula In A Macro To Sum Same Range All Ws

I have a workbook that will have a different number of sheets every time. All of the sheets have the same format. I have a summary sheet in which I would like to sum the total of Sheet1 thru the Last sheet in every cell from B12 to B24, then I am going to move on to other columns.

I am getting the same error everytime "Object doesn't support this property or method" and the error is #438.

I have tried different formulas, but none of them are working. Here is my code......


Sub FillSumSht()

Dim wb As Workbook
Dim sSheet As Worksheet
Dim LstShtNm As String
Dim LstSheet As Worksheet
Dim TotalSheets As Long
Dim s As Integer
Dim n As Integer