In the absence of any information about what you have tried already something like this should work:
Dim sumTotal as Integer
Dim NamedRange as Range
Set NamedRange = ActiveSheet.Range("NameOfRange")
'Find the Bottom Right Corner
sumTotal = sumTotal + NamedRange.Cells(1, 1).Offset(NamedRange.Rows.Count - 1, NamedRange.Columns.Count - 1).Value
'do this for each NamedRange