Oracle Internet Expenses : Invalid GL Account Combination.

Hello There                   We have OIE:Enable Expense Allocations set to Automatically-enabled, with Online Validation and are trying to create project based expense on 11i. The system allows to use the combination of Project/Task/Expenditure org which will generate invalid CCID during the approval process. We want to restrict the processing of this expense before it's submitted to supervisor for approval. Is there any way out of the box by which system can restrict this ?

If not, at what place should be put this validation - AP_WEB_CUS_ACCTG_PKG.BuildDistProjectAccount or AP_WEB_CUST_DFLEX_PKG.CustomValidateLine?

Thanks