compute figure

[wilson Peterson]

Column A Column B Column C
Scenario A $ Depart Code
Debit Books 40 1010521
Credit Bank 40
Debit Computer 500 1010741
Credit Bank 500
Scenario B
Debit Books 40 1010521
Debit Computer 500 1010741
Credit Bank 540
Problem A
Could anyone suggest a macro that combine both expenses
(Computer & Books) into one amount with only one credit line
entry as shown in Scenario B(only for depart code 1010521 &
1010741).
Question:what's the source code?
Problem B
Can I create a macro that verify whether user entered a valid
depart code by matching the code entered in Column C against
a database table that contained a list of valid depart code.If code
entered is not in the database,a pop-up message box will prompt
the user to re-enter a valid depart code in Column C or in a
textbox form repeatedly until a valid depart code is accepted.
Let's us assume that depart code 1010521 is an invalid code.
Question:Any source code for this?
Problem C
A macro program that can automatically compute finance charges
figure if amount entered in Column B is within $5 to $40 based
on 1.5% rate,and 3% if amount is more than $450 but less than
$600.Let's assume finance charge in Scenario B need to be computed
The computed figure (1.5% X $40) & (3% X $500) has to be
automatically Debited immediatelly below or above the Credit line
related to Bank.
Question: Any source code for this?