How do I calculate NORMSINV ??

I am trying to convert/replicate a Excel spreadsheet into a method in Xojo. In one formula there is the function NORMSINV. I have no idea how to replicate that within Xojo. Please keep in mind that I never took any statistical courses. So, I have no idea what it means.

Thanks for any insight.

Here’s a VB version that ought to be easy enough to translate:

Fantastic Paul !! That will definitely help.

Much obliged.