vb08 disable a textbox>> yes or no <<

hello all i am making by autotalker better now i wanna make a choise option with 2 radiobuttons like:

radiobutten1: use 1 textbox
radiobutten2: use 2 textboxes

i got a form that has a interval in seconds some labels and 1 timer 2 buttens and 2 textboxes

now i try to find the code to disable a textbox googled like a hour but couldnt find anything can some1 help me ?

here is my coding:



please help me !