NEED ADD-ON

Hi to all Hope someone can help I need an add-on with the following Create a credit that affects the tax table Applicable to a specific transaction So that the transaction is adjusted automatically In the account aging example CUSTOMER #- 12333 = A NAME- JOSE MORALES = B COMPANY -JMM = B ACCOUNT BAL- 1500 = B TRANS NUM- 78523 = C TRANS BALANCE AMOUNT- 107.61 = D TRANS TAX AMOUNT FOR TRANSACTION 43.61 = E ACCOUNT CREDIT 64 = F TAX CREDIT- 43.61 = G CITY 5.5 - 32.51 = H STATE 1.5 - 11.1 = I NOTES COMMENT 123 = J APPLY = K PRINT = L A=LOOK UP CUST B=AUTO FILL NAME B=AUTO FILL COMPANY B=AUTO FILL ACCOUNT BAL C=SELECT TRANS NUMBER ENTER OR LOOKUP D=TRANS BALANCE FOR THIS TRANSACTION NUMBER E=TAX AMOUNT FOR THIS TRANSACTION F¬COUNT CREDIT CUSTOMER ENTERED G=TAX ADJUSTMENT AMOUNT TOTAL CUST ENTERED H=CITY 5.5 .79% OF (G) CAN BE CHANGED I=STATE 1.5 .21% OF (G) CAN BE CHANGED J=COMMENTS 256 LONG K=APPLY TO ACCOUNT IMMEDIATELY L=PRINT INVOICE WITH ORIG TRANS BAL AND NEW TRANS BAL - ALSO ACCOUNT BAL NEW PART 2 HOW TO APPLY JUST ONE CREDIT TO A CUSTOMER NOT ALL AT ONCE