Urgent Help : Visual Basic

My assignment.
Create a program that lets the user type a sentence into a text box, click a button, and then the program tells the user exactly how many A E I O U’s there are in the scentence.

My problem.
I can get the data saved into a variable easy enough, but what code do I use to calculate just how many A E I O U’s there are?

My plea.
Please if anyone knows how to acheive this, I would be very grateful if they could just post the information in this thread…

Thank you very much !

P.S, Ill love you long time !