Adding Message Prompts

Hi,

One of my colleagues wrote a new function and I'm trying to add some prompts to the function. For example, when you begin typing =SUM it shows a message box in Excel that says:

"Adds all the numbers in a range of cells"
I need one that says "Returns the Point-Biserial product moment correlation coefficient, rpbi"

Also, as soon as the open parenthesis is added to a function then you get hints for the values that go in each spot.

=SUM( has a prompt that says "SUM(number1, [number2], ...)"
I need one that says "point_biserial(biserial_array, continuous_array, [success_value],[nonsuccess_value])"

How do I create these for my function? Thank you for all your help!! Let me know if I need to send you the VBA.

Thanks!!