[Boofo]

You are the man! Thank you!

I was way off on the regex as I suck at those. Here is what I ended up using:

	if (!(strlen($vbulletin->GPC['letter']) == 1) && preg_match('/^[a-zA-Z0-9]+$/', $vbulletin->GPC['letter']))
	{
		print_stop_message('cannot_have_null_values');
	}

I will be using a different stop message, but I wanted to make sure I could get it to work first. I have another condition before this one that checks to make sure all 3 variables (letter + 2 others) are not blank. I was going to add this to that but I wanted to catch the letter variable separately. This is how it all looks together for the error checking:

	if (!$vbulletin->GPC['quote'] OR !$vbulletin->GPC['name'] OR !$vbulletin->GPC['letter'])
	{
		print_stop_message('cannot_have_null_values');
	}

	if (!(strlen($vbulletin->GPC['letter']) == 1) && preg_match('/^[a-zA-Z0-9]+$/', $vbulletin->GPC['letter']))
	{
		print_stop_message('cannot_have_null_values');
	}

If you have any suggestion s or advice, I am all ears. And thank you again.