FI Substitution rule on completed document

Question

Hi Everyone,
We're trying to create a substitution rule to change the payment terms on our invoices (fields BSEG-ZTERM and BSEG-ZBD1T).  We're having trouble with our prerequisite:  If any of the expense distributions are being charged against a federal grant (BSEG-GRANT_NBR) then call the substitution rule.   We want our exit to loop through all distribution lines and if it finds any being charged to a grant it should set the condition to true and substitute...if it doesn't find any it should be set to false. 
We've done all of the necessary steps:
-Activated the fields on GB01
-Defined the substitution rules on OBBH
-Build and compiled the user exit.
Problem we're having is that when there are multiple lines it only seems to be reading the last line item to make the determination.
Example 1:
Line 1 Grant
Line 2 No Grant
Result is that payment terms are not substituted.  It should be substituted because line 1 hit a grant.
Example 2:
Line 1 No Grant
Line 2 Grant
Result is that payment terms are substituted correctly. 
My ABAPer says that the problem seems to be that on the completed document he can only see the last line (not all the lines)....does anyone know a way to loop through all the records on a completed document?  It seems that substitution gets called before records get inserted into the database so we're not sure how to make our pre-requisite work.
thanks for your help

Answer 1

Hi,
here is the solution.
Create your user exit.
FORM u280 USING bool_data TYPE gb002_015.
FIELD-SYMBOLS: <ls_bseg> LIKE LINE OF bool_data-bseg,
LOOP AT bool_data-bseg ASSIGNING <ls_bseg>.
* Here is your logic needed
ENDLOOP.
Create a substitution for the complete document in GGB1 and choose no field but "Only exit'.