TINV Excel function in C#....HELP

[AluminumHaste]

Hi a friend of mine is doing a program in which he needs to use the TINV function from Excel but in a C# program.
I've googled but I can't find the formula and how to use it.
In VS2005 I found in the help that you can use the Microsoft Excel interop namespace to get at the TINV function but implementing this using the example provided doesn't work at all.

Can anyone help me with this?

 

[Zenitram]

what does TINV do exactly? Mebbe there is another function that does the same thing as this "TINV" but named differently.

 

[AluminumHaste]

It's a T-DISTRIBUTION INVERSE-PROBABILITY function. And I think I just found the math behind it.