GL Lines --> COM History

Hello,
Can someone tell me how to link G/L Lines (YAA7REP) with COM History File 
(MBBWCPP)? I have a simple query and here is what I have done:
1. Used the Admin Div/Transaction ID to link to the G/L Lines (YAA7REP) to its 
Transaction Header (YAARREP)
2. I have selected unit, nature, transaction number and Gn/lg line narrative as 
my fields

Basically, the transaction number is '00' followed by 4-digit invoice number 
(e.g.-002568) OR '0' followed by 5-digit invoice number (e.g.-012548). The 
Gn/lg line narrative contains for example -  'CO   38  Customer order',  'CM  
38  Credit memo' etc.

I know that I can manipulate and reformat either the transaction number and 
link that with invoice number in COM History File or reformat the Gn/lg line 
narrative and link that to quote/order number in COM History File.

So far I've been downloading these two data sets - (G/L lines+ header) and COM 
history into Access DB as it's easier to do the required manipulation (I've 
been chopping off the 0's from transaction # to get invoice number) there and 
get the desired results. It works great.

I was wondering if someone knows how to accomplish this manipulation in 
query/400. Thanks in advance.

Thanks,
Nandu