Requirment of two records in One Idoc

Dear Expert

Requirement is such that like:

Currently there is one condition Record in system as :

Site Vendor Article Tax Valid From Valid To Tax Code

111 100000 2000000 5% 01.01.2011 31.12.999 V0

Now User Inserting A new record As ;

111 100000 2000000 10% 11.11.2011 31.12.9999 V0

In this case if we triggered data through BD21 , Two Idoc are generating form SAP for Both Change Records

But Client requirement is such that both change records should flow in One Idoc.

How it can be done , what are those setting in SAP.

Thanks & Regards,

Surendra