JQuery :: Transforming Change Function To Validator AddMethod Rule

I wrote this function to be a change event applied to a checkbox. Now it is apparent I need to use it as a custom validator method, so it runs when you hit "Next" to step through the form. I have all that working, I just can't get the syntax of the rule right.

Here it is as a change event:
$(
'#MKDPT'
).change(
function(){
if(
$(
'#MKDPT'
).is(
':checked'
)){
var
checked
=
false
; .....

And my attempt at a custom validation rule:
$
.
validator
.
addMethod (
"MKDPTOnly" ,
function (
value .....

I have tried several versions, but none is letting the form go to the next step (return true) if the conditions are met.