How to call What-if data table as a function or procedure?

Hi,

I built a mini worksheet to calculate tax amount, where I enter a gross income in a certain cell and get the tax amount as a result in another cell. Now I want to develop it one step further to use the calculation as a function or procedure to be called from another worksheet/file. It would look like a user defined function "CalculatedTaxAmount(Gross_Income)" where I give it variable "Gross_Income" and it will return a tax amount as a result. Existing What_If data_table can help me to get a half result only (still not be able to call from another worksheet). 

Appreciate any help/support for my idea.

Thanks