Require only one check for grid question

Challenge

Normally, the grid question require one answer for each sub question to navigate to next question. Now, we want it require only one check for the whole grid.

Example

Script

 1 var normalQuestionCheck = questioncheck;
 2 
 3 function extendedQuestionCheck()
 4 {
 5    ErrorMessages.getInstance().clearErrorMessages();//clear old error message
 6    var valid = false;
 7    var q_name = "QUESTION." + "GridQuestionLabel";//question's name = "QUESTION." + question label
 8    var n = $(".grid_inner")[0].rows.length - 1;//number of sub questions
 9 
10    //check if each answer option for each sub question is checked
11    for(var i=0;i<n;i++)
12 	{
13 		$("input:checkbox[name='"+q_name+"."+i+"']").each(
14 			function()
15 			{
16 				if($(this).attr("checked"))
17 					valid = true;				
18 			}
19 		);
20 		if(valid)
21 		break;
22 	}
23 	
24    if(!valid) showError(quest.requiredtext);
25    return valid;
26          
27 }
28 
29 function showError(e)
30 {
31    ErrorMessages.getInstance().showErrorMessage(e);
32 }
33 
34 questioncheck = extendedQuestionCheck;