Regular expression validation

I am using a regular expression validator to check for maximum lenght in my multiline textbox.  I am also using javascript to now allow users to enter any text if max lenght reaches 1000.   But it does not appear my regular expression validator is not working because it is not throwing up the error that you have exceeded maximum character lenght of 1000.    Now, it was sort of working before I put in this javascript code.  What happened before is that you could keep typing in the textbox and once you clicked out of the textbox the message would appear that you have exceeded 1000 characteres.    I would like that message to pop up right as they have reached that 1000 character input. 





Java Script

    function checkMaxLen(txt,maxLen)
    {
        try{
        if(txt.value.len ...