How do invoke a Tk button to a procedure in C.

[KumarSree]

Hello

I have written a program in C using MS VC++,to which
i have added extensions of Tcl/tk.I am able to get
a Tcl interpreter and also a widget on which i am able to place buttons.

But the problem i facing is how do i invoke a procedure
by pressing a button.Suppose i have written a command
say cube of number.
I am able to get it run using the tcl interpreter,but
i want to do the same by just pressing a button after
giving the required input.
Hope u understood my problem,sorry the message was long.

Could u give a example for me .
maybe a small program .
Thank u.