How to find and set a value into a field from another form?

How to find and set a value into a field from another form?

I have 2 forms.

On occasional basis, I add new name into the first form and assign particular tax rate and commission to that name.

Daily, I need to enter data into the second form. I choose a name from "lookup/drop down" menu connected to the first form and fill out couple numbers. The form calculates the rest. What I need is, depending on the name I select, to automatically look up and fill the tax and commission that were set in the first form.

What would be the best way to accomplish this?

Thank you!

Daniel