Query request for access 2007 (2003 format)

[Txl]

Hello all,

I have a table with a few fields including an "amount" field for an
operation

I would like to compute automatically the variations of the balance
corresponding to the amounts as they change

Something like this

Operation amount balance
1 1000 1000
2 -500 500
3 -900 -400
4 2000 1600

Ans so on

I would like the balance to compute itself but I don't know how to do
it because I need to get the value of the previous record to do
something like

"balance (n) = balance (n-1) + amount"

and I can"'t do it, I've tried with dlookup, with vba and moveprevious
and so on and I can't make it work...the syntax of access only seems
to get worse and worse with each new version....

I need to keep the "history" (ie the values of the balance in the
records 1-3 because I want to make a graph of it

Thanks a lot for the help