Formula fields addition

I have the following issue in Crystal Reports 10:

we are doing a crystal report with the following format:
Account            Description      Beginning Bal      Current Balance      Ending Balance

The user chooses a period..let us say 200404.
The logic is as follows:
Beginning Balance contains the sum of all account amounts for whole of 2003 ie., 200301 to 200312 plus all account amounts till april 2004 ie., till 200403.

current Balance contains all account amounts for the current period ie., for 200404 ie., only for the month of april.

Ending Balance is sum of Beginning Balance and Ending Balance.

This should be for all account numbers.

the these account numbers are grouped by ranges as total expenses,total revenues,total income etc.

The problem is all the account amounts are stored in a field called BAMOUNT. This stores both positive and negative values ( for debit and credit values).

How do we get this right:

Format:

Account            Description             Beginning Bal      Current Balance      Ending Balance
11001            xxxxx            2500            3000            5500
12001            xxxxx            3400            3400            6800

Total Liability                  5900            6400            12300

like the above format we are having lot of groups.

we have done some logic which checks the input period and picks up amounts for each account number from the previous period and upto the current period, ignoring the sign and placing it right.

same way for current balance also.

but when we are trying to add beginning balance  to current balance to get the ending balance we are getting erroneous results.

all three of them are placed in group footer with detailed section supressed.

please give me a solution for this ASAP.

so how do i get the whole thing right.



expecting a detailed response.