Fill the textbox

Question

Hi!

 

textbox and button:

 

I have a textbox that I limited the maxlenght to 10 caracters.

Then if I insert for example 3 caracters its will left 7 blank or white spaces. This 7 blank spaces left I need to be filled automatically with a "---------" until at  the maximum of 10 caracters. 

In other way, each number of caracter(s) inserted cannot have blank space letf inside of the textbox. Otherwise should be filled with this line "---------".

But if I insert 10 caracters then there is not need to fill the rest of my textbox.

 

Many thanx