Regrading the refresh values in text box

Hi friends,

i need to refresh the values in my text box in run time.

I created a text box,and set the validation for that text box(range of values only it will accept Ex.60-70)

after checking validation in run time the value in text box will refresh, if it is in valid value

1.how to refresh the values in text box after checking the condition

2.how to set the validation for a text box?

plz send code related help.....

Thanks & Regards

SARAN