How can I make my character counter display how many characters are left on page load. Right now it only displayed the number of characters left when I user keysup, keysdown or onblurs.

Code JavaScript:
                var companydo	= document.getElementById('cscompanydo');
		function validate_companydo_field_length() {	
			var len = companydo.value.length;
			var mc = 2000;
			if (len > mc) {
				companydo.value = companydo.value.substring(0,mc);
				len = mc;
			document.getElementById('doremaining').innerHTML = mc - len;
		companydo.onkeyup		= validate_companydo_field_length;
		companydo.onkeydown	= validate_companydo_field_length;
		companydo.onblur		= validate_companydo_field_length;

Code HTML4Strict:
<textarea class="medium mediumwidth man" id="cscompanydo" name="companydo" rows="" cols=""><?php echo $answer['companydo']; ?></textarea>
<div class="f_right mts mrs"><span id="doremaining" class="mrs">2000</span>characters remaining</div>