Dependent Replacement Formulas

Hi,

I would really appreciate any help on this as i am going mad from this problem!

I am trying to write a macro that will do the following for me but everything i seem to be doing wont work!! Here is basically what i want it to do:

If Cell A1 = "H" then Replace Cell B1 with a "String".
(Ideally "H" and "String" would be arguments in my function).

On top of this (!!) I would like it to work in such a way that this operation would be repeated for each row in a certain range, e.g. rows 1 - 10.

I have tried to write code for this with disastrous results. I could post it on this site but I feel intimidated by everyones know how and dont want to get laughed at!!

Once again, thanks for any help,
TB