Trying to create a running total

[Nphp0729]

I am trying to create a query that will give me a running total by product grouping and serial number. I currently have these three fields Products, Serial Number and Order Quantity. I've played with IIf and DSum but don't get what I am looking for.
This is what I get.
Products Serial Number Order Quantity Running Total
00053 0001 2 3
00053 0002 1 3
00047 0001 3 4
00047 0002 1 4
00026 0001 5 10
00026 0002 3 10
00026 0003 2 10

This is what I am looking for....
Products Serial Number Order Quantity Running Total
00053 0001 2 2
00053 0002 1 3
00047 0001 3 3
00047 0002 1 4
00026 0001 5 5
00026 0002 3 8
00026 0003 2 10

 

[vbaInet]

Have a look at this thread. There are a couple of suggestions.
http://www.access-programmers.co.uk/forums/showthread.php?t=189241&highlight=running+total

 

[Nphp0729]

I took a look at that thread. He is not looking to achieve the same results. He is looking for a count where I am looking for a total. I need my to seperate it by group but also sum the previous qty with the new qty.

 

[vbaInet]

It's the same concept and it was given to inspire you. Be inspired

Use what is given and lookup the DSum function.