How to get a sum of columns if criteria is met?

[mtbthepro]

Hello, how would I go about to modifying this code so that it will calculate the total of all the account totals? The code below is below is supposed to look for account totals in each department in each sheet and if that department has more than 1 account total the macro will give it a "grand total" at the end of that department but the grand total doesn't have numbers in it. So how can I gather the number from the account total and sum it into grand total.

Sub AddGT()  
    Dim ab As Range
    Dim i As Long, lRow As Long, j As Long
    Dim Streak As Integer
    Dim sht As Worksheet
    Dim wsn
    Dim nam As String
       
    Application.ScreenUpdating = False
    wsn = Array("Francisca", "Lucria", "Alberto", "Amanda", "Early Child", "Melanie", _
            "Natasha&Tom", "Maria", "Jess", "Grosv KDGN", "Tashana", "Space Rental")
      
   
       
    For j = LBound(wsn) To UBound(wsn)
        nam = wsn(j)
        Worksheets(nam).Activate
        MsgBox ActiveSheet.Name


        lRow = Cells(Rows.Count, 2).End(xlUp).Row
        Set ab = Range("B1:B" & lRow)
           


        For i = 1 To ab.Rows.Count
            If ab.Rows.Count = 1 Then Streak = 0
            If ab(i).Offset(0, -1) Like "Department*" Then
                If Streak >= 2 Then Cells(ab(i).Row - 1, 3).Value = "GRAND TOTAL"
                Streak = 0
            End If
            If ab(i) = "ACCOUNT TOTAL" Then Streak = Streak + 1
        Next
        If Streak >= 2 Then
            Streak = 0
            Cells(ab(i).Row + 1, 3).Value = "GRAND TOTAL"
        End If
    Next j
   Application.ScreenUpdating = True
End Sub