Setting Default Values for Forms from parms passed in URL

I'm trying set a field of a form built with FB using a parameter passed on the URL that invokes the page containing the form.

Contactemail.php?mls=54321&rid=100

As you can see I have two fields mls and rid. I've edited the code that is created by FB to set the default value of two fields MLS_Number and Realtor_ID. I was thinking that I could simply reference the parameters $mls and $rid or use $_Get["mls"] or $_Get["rid"]

The code below....doesn't provide any value for the MLS_Number field....but if I just use "111" directly for the value of Realtor_ID" the string does show up in the proper field in the form....but its not the value passed on the URL.

Any suggestions....I suspect this is a simple problem...but I'm a newbie.

Thanks

<input id="MLS_Number" name="MLS_Number" type="text" value="<?php echo((isset($_GET["mls"])?ValidatedField("Contactemail","MLS_Number"): $_Get["mls"])); ?>" class="formTextfield_XSmall" tabindex="6" onblur="hideServerError('MLS_Number_ServerError');"/>
<span class="textfieldRequiredMsg">Please enter your email address.</span> </span> </div>
</div>
</div>
</div>
</div>
<div class="lineGroup">
<div class="fullColumnGroup">
<label for="Realtor_ID" class="sublabel" > Realtor ID</label>
<div class="errorGroup">
<div class="fieldPair">
<div class="fieldGroup"> <span id="Realtor_ID_Spry">
<input id="Realtor_ID" name="Realtor_ID" type="text" value="<?php echo((isset($_GET["invalid"])?ValidatedField("Contactemail","Realtor_ID"):"111")); ?>" class="formTextfield_XSmall" tabindex="7" onblur="hideServerError('Realtor_ID_ServerError');"/>