JQuery Validate - Message tailoring

JQuery Validate - Message tailoring

Hi everyone. I recently came across this wonderful validate plugin

I've worked out how to modify the rules based on values in other fields, but wondering if the error message can be tailored in a similar fashion

eg
  1.         rules: {
  2.             myname:        { required: function(element) { return $("#mpAdType").val() != "Buy"; }},
  3.             },
  4.          messages: {
  5.             mpAdType:    "<span class='f00 strng'>Please select an option</span>",
  6.             mpTitle:    function(element) {
  7.                             if ($("#mpAdType").val() != "Buy")
  8.                                 return "<span class='f00 strng'>Please enter a name of your thingamajig</span>";
  9.                             else
  10.                                 return "<span class='f00 strng'>What is the name of what are you looking for</span>";
  11.                         }.
  12.       }

Basically it's a form with 2 versions of Sell (with/without pictures to be uploaded) or Buy stuff
The "myname" field ends up required if the "mpAdType" field is NOT Buy (we dont charge for Buy ad's)

But I want a different message based on the Ad Type. This doesnt work...

Thoughts anyone ?