Here's one way (you have to select the whole column, excluding any headings
and down to the third cell below the final number group):

Sub mySum()
   Dim myCounter As Long
   Dim myTotal As Double
   myTotal = 0
   myCounter = 0
   Do While myCounter <= Selection.Rows.Count
       If ActiveCell.Offset(myCounter, 0).Value <> "" Then
           myTotal = myTotal + ActiveCell.Offset(myCounter, 0).Value
       Else
           ActiveCell.Offset(myCounter + 2, 0).Value = myTotal
           myTotal = 0
           myCounter = myCounter + 3
       End If
       myCounter = myCounter + 1
   Loop
End Sub

Name your ranges rng1, rng 2 rng3, etc then use the following code:

Sub SumRngs()
Dim RngRows As Long
Dim c As String
Dim rngsum As Range
Dim cntr As Long

For cntr = 1 To 3
RngRows = Range("rng" & cntr).Rows.Count
c = Range("rng" & cntr).Address
Range(c).Range("A1").Offset(RngRows + 2, 0).Value =
WorksheetFunction.Sum(Range("rng" & cntr))
Next cntr
End Sub

MIke F