Data from all cells in a range

[jn_mohit]

I am writing a program which would take in a range as an input and do some calculations from the value of cells in the selected range.

I am able to get this as long as I give a single range as input but i get an error for range with multiple areas. What could be done about this.

Here's simplified version of my program (which only calculates SUM but that is not what I want to do)

 
    Dim rRange as range
    running_total = 0
    set rRange = Range("A1")
Dim rcell As Range
    For Each rcell In rRange
           running_total = running_total + rcell.Value
    Next rcell

if I set 
 rRange = Range("A1:A10") ---- Pass
rRange = Range("A1, A2, A3") ---- Fail
rRange = Range("A1:D10") ---- Pass
rRange = Range("A1:A10,D1:D10") --- Fail

Please let me know how can i get around this.

Thank you