Total SUMS based on a seperate dependant, within the same column!

Hi All

I have wracked my brain about this for about 2 days now and I just cant figure it out.

I have attached a form to show what i have. The table on the right hand side is reflective of the key items numbers in the table on the left. What i need is for each of those numbers in the right hand table to show the sum amount of quanities that appear in the left hand table for that specific number.

So Item 1 in the right hand table should be equal to 2 as the sum of the quantity values for key item 1 in the left hand table is 2.
Item 2 in the right hand table should be equal to 7 as the sum of the quantity values for key item 2 in the left hand table is 7 and so on...

Any help would be MOST appreciated.

Thanks

Fantastic

thank you