Number and Alphabet validation for textbox

HI every one

I have two Text box and one button  in my page.

in TEXTBOX 1 user should enter NUMBER and in TEXTBOX 2 they should enter word i want if user in TB1 enter otherthing than NUMBER in Message box show "please enter number" 

and  if in TB2 they enter otherthing than Alphabet in Message box  show "please enter  Alphabet"

it should happen when user click on button how i can do it?

thanks