Hi I'm modifying my contact_us.php form to include extra text boxes for the customer to fill in... that's the easy bit :)

I've gone through lots of scripts for php contact us pages, but none I found have the function I'm looking for

I want to force the customer to add text to various text boxes, then if left blank, to give an alert message. I tried pasting in my existing html form from my existing html site, but the alerts don't work correctly when pasted into a php page. Most of the contact_us scripts have alerts for the email address, but my attemps to replicate this with mods has not worked.Can anyone help me on this please?

I can post what I already have if that helps?

Thanks in advance