SSRS Total of the textbox values

I have prepared a report which shows the payments. The payments are grouped first on the departments and then managers and lastly the project names. There is a short demonstration below.

Herein, I have written custom code functions for calculating Total and Department Totals. They work. Because they are in the groups. HoweverSUM is not in a group. That means SUM is just in the end of report. It must sum all thedepartment totals. As you can see above it must be 4350. Also, I have written a custom code function to calculate the sum of allDepartment Totals. But, it just calculates the last group's Department Total. It means, my custom code for SUM shows me650. My custom code is below. Please have a look. I am trying to solve this since this morning..

Public Function CalcMedTotal5(ThisValueeeee as Integer) as Integer

    GroupMedTotal5 = GroupMedTotal5 + ThisValueeeee
    GrandMedTotal5 = GrandMedTotal5 +ThisValueeeee

End Function

Public Function ReturnMedSubtotal5() as Integer
    Dim ThisValueeeee as Integer = GrandMedTotal5 
    Return ThisValueeeee
End Function

KAdir