Manually delete rebate condition record in Sales order

Dear SD gurus,

I have a requirement from business to be able to manually delete a rebate condition record from the sales order line item in some cases, where they see rebate is not applicable. I have tried different options as below:

1. Pricing procedure don't have these rebate condition types mandatory.

2. In V/06, I changed settings for "Changes which can be made" to both 'A' & 'B'.

3. After making above changes, I tried creating new sales order & then tried to delete the Rebate condition record.

FYI.. I am running SAP 4.6C .

Really appreciate a quick reply.

Thanks

Suri