Thanks for your reply. I have all the values stored in the workbook:
1.income - i type it in in cell A1
2. kids - i have them stored in a Data Validation list (no of kids
ranges from 0 - 4, everything above 4 is treated as 4)
3. about deductions, i have them stored in the same workbook on 5
colums, depending on no of kids.

Let me give you an simple example:
for income 500 and kids=2, the dedction is 20.
for income 500 and kids=0, the deduction is 10.
As you can see, the relationship between income and kids, on one hand and
deduction is like this: the higher the income the lower the deduction, based
on how many kids you have at home.

Anyways, thanns again for your help.