Posting to FI 9999 Line Items

Dear Experts,

i am doing collective billing for the period of 30 days. for 5 line items. while posting to invoice system is giving error Max No line items i.e 9999. I want to group for eg. in teh billing document Material XXXXX is comming 100 times and posting is also happening 100 times for the same GL. I want system to clud Net value of Material XXXXX for 100 line items and post to G?. nuthing but grouping if line items and posting to GL.

Please do the needful an