Tax on Sales & Purchase exclusive of Base amount

Dear Friends,

My client requirement is that SAP system should calculate the Service Tax amount on the Base amount , that is , Base amount should be exclusive of service Tax. For ex. If I put Rs 1000.00 in amount field in FB60, System should calculate tax on Rs 1000.00…… Rs 100 , say 10%, on Rs 1000.00. and Entry should be—

Customer Account Dr 1100.00

Income account Cr 1000.00

Service tax a/c Cr 100.00

I tried with FB00 as tax calculate on Net value but no success. Please help me out.

Regards

Manish