Excel maro macro to look up a closed excel function workbook.

I have a workbook with several sheets which contains a very long and complicated function.
What I want to do is:
First enter a value in Cell A, for example: 5%
Press enter
Then I could get the answer (for example 89) from Cell B.


the worksheet will be used frequently, since I have a lot of values to look up and I don't want to open it.(since I have a lot of similar fuction workbooks)

Can I use macro to achieve this:
I create a worksheet-- column A has the values to look at, and I can run a macro to get corresponding functional values of column A.


Could anyone give me some help????