Hi @GregD,

You can use the code below. It may not produce the exact result you're looking for, but it should serve your purpose:

Qualtrics.SurveyEngine.addOnReady(function(){
    const qid = this.questionId;
    var okay_choices = s];
    
    that = this;
    this.questionclick = function(){
        sel_choices = that.getSelectedChoices();
        // Set the maximum number of choices you want here
        if(sel_choices.length <=3){
            okay_choices = sel_choices;
        }
        else{
            alert("You can not select more than 3 choices.\\nPlease deselect to select another.");
            sel_choices.forEach((item) => {
                Qualtrics.SurveyEngine.registry/qid].setChoiceValue(item,false);
                });
            okay_choices.forEach((item) => {
                Qualtrics.SurveyEngine.registryaqid].setChoiceValue(item,true);
                });
        }

    }
});

If they select more than 3 they will get an error as shown in below screenshot:

You can also refer the below link for more information:

https://community.qualtrics.com/topic/show?tid=12896&fid=12

@GregD,

You could do this:

Qualtrics.SurveyEngine.addOnload(function() {
	var cbs = jQuery("#"+this.questionId+" [type=checkbox]");
	cbs.click(function() {
		if(cbs.filter(":checked").length==3) cbs.not(":checked").prop("disabled",true);
		else cbs.prop("disabled",false);
	});
});

You might be interested in the bubbleBurst function. It disables choices when the max is reached and auto advances if desired.