Enable delta in custom fields - datasource 2LIS_02_ITM

Dear Gurus,

I have a requirement for capturing account assignment information of outline agreements (contracts) in Purchasing info-cube. So I did the following steps :

1. Append MCEKPO

2. Maintain Extract Structure MC02M_0ITM

3. Maintain enhancement in LEINS001

Every works ok when executing setup of statistical tables. But when the user changes only the account assignment of an outline agreement , without changing any other fields (e.g quantities), no delta record is generated.

Any suggestions?

Thank you in advance for your help.

Dina