need help with jquery ajax form field valiation against database

You can try this, and for the CFC method using javascript you can look here :

http://help.adobe.com/en_US/ColdFusion/9.0/CFMLRef/WSc3ff6d0ea77859461172e0811cbec22c24-79f9.html

ITs not perfect, and probbly will need some twekaing ,,,, but its somthgin to start from

<script type="text/javascript">
var formSubmitFlag = false;

// Function that is binded to the keyUp of the textbox
function onTextboxChange(textValue)
{
if(textValue.length == 6)
{
  alert('6 carecters - '  + textValue);
  // Do validation here ...
  // You can use CFC with java script
  // and if its validated change the formSubmitFlag = true so the form can be submited
  formSubmitFlag = true;
 
 
// end if
}
// End function
}

// Form submit control
function checkFormSubmitFlag()
{
if(!formSubmitFlag)
{
  alert('Can not submit yet until the field is validated ...');
}

return formSubmitFlag;
}

</script>

<cfform onsubmit="return checkFormSubmitFlag();" name="myForm">

<cfinput type="text" name="mytextbox" onKeyUp="onTextboxChange(this.value);">
<input type="submit" />
</cfform>