If the report can have more than 2 groups, do you want the total from _only_ the group right before that one, or do you really want the total of all of the groups (records) up to that point?

 If you want the total for everything up to that point, a running total may be all that you need.

 James

IdoMillet your answer works but not fully
the total that i got in the second section was not right

James0628 the report has 1 group which is group by date

Tough to guess what is wrong without more detail.
Explain what formula you have in what section and at what point you get a value that is not as expected.
Use images if possible.

so that is the way the report is designed 1 group by date
the point of this report is to show in the first section the sum of the payment from the begging of time till the day the user choose and in the second section the payments done from the day desired till present day
the first section will only show the sum and the second section will show the details as well as the details
the trick is that i need the total of the first section to be used in the difference of payments as your code did but the sum displayed in the function isn't the sum of the first section
thank you in advance

the point of this report is to show in the first section the sum of the payment from the begging of time till the day the user choose and in the second section the payments done from the day desired till present day

Define "first section" and "second section".

the first section will only show the sum and the second section will show the details as well as the details

"... will show the details as well as the details" ?

 James

Show the details as well as the Total** sorry for the mistake
anw i found an alternate solution using the running total in the query

So you've got the figures that you were looking for?  Glad to hear it.

 James