count the textbox characters?

Question

Hi!
I am taking one TextBox and Lable. label Text is 150. and i set TextMode is Multiline and MaxLength is 150. My aim is when i write text in textbox. that text count is displayed in label. when user erase the text that time also count decrease. how to write code to do this.
and one more thing. i set Multiline to textbox and max length is 150. if i enter more than 150 characters it allows. but my aim is it not allow, enter 150 characters then we enter words it not print. how to write program to do this?
Thanks.