I have a workbook with a macro, and I'm going to use the macro to open a different workbook called "filename." Once this second workbook has been opened, I'm going to sum column AJ, and then I'm going to use that value to copy and paste the total value into cell C29 on the first workbook. This will all be done using Excel and VBA.
Sub vba_open_workbook()
Application.Calculation = xlCalculationAutomatic
filename = Range("G11")
Workbooks.Open filename
Workbooks(1).Activate
Range("C29") = Application.WorksheetFunction.Sum(Range("AJ:AJ"))
End Sub