to make a timer in c#

Question

hello everyone, I have a big problem. I need to make sort of a GSM with a timer. I've got 10 buttons, from 1-10 when i push on the first button I most get the "a" in a textbox. If i click again on the first button but it is shorter then one second I need to get the b, and so on... So it most be a timer, no longer then 2 seconds everytime that i click. Can somebody help me please? thx Annie