Is there a trick to setting up a custom help function?

I have a spreadsheet templates to which I have instructions / comments for
cell headings (rows& Columns). Is there a way to setup so that when a user
presses F1 or some other user defined F4 key that the instructions will popup.

My instructions are in a word file, and my logic was some sort of "search"
on the cell contents or define when F4 is pressed that it goes to a specific
bookmark in the word document.