How do I customize POR_CUSTOM_PKG to prompt user to enter correct charge account

Hi,

We have a requirment for prompting user to enter charge account while creating a requstion for Expense items only and before they approve it.

I found a note on metalin saying this can be achieve by customizaing package POR_CUSTOM_PKG.

Does anyone have suggestions how to customize it?

Thanks in advance.

Thanks,

Rajesh