A Valid post code gives a drop down select in a form

[scotchegg78]

guys

 

I have a form, and inparticular an input box ..

 

	<p class='label_field_pair'>
	<label for='postcode'>Postcode</label>
	<input type='text' name='postcode' id='postcode' value='".$carerregistrant->postcode."'/>


</p>

 

now on submit of this form a 2nd page come and based on the users post code a radio list appears and the user selects their closest postcode, this is all done already.

 

But i need it to instead of apperaring when a user submits the form a live validation of postcode and when valid the radio options drop into view.

 

I understand i may need to use JS and regualr expressions to validate the postcode, and then somehow drop down a new form option into view? Anyone done anything like this before?

 

thanks

[scotchegg78]

I would add i think i have the regular expression ..

[A-Z]{1,2}[0-9]{1,2} ?[0-9][A-Z]{2}