JavaScript to validate checkboxes

This JavaScript to validate a form works for all input fields except my checkboxes. What the user
should see when they click the submit button -- assuming they leave form fields blank -- is an alert
box with short messages indicating which fields were left blank. Each of those form fields has it's
own function and "why +=" line, but I removed most of those for the sake of brevity. Here are
snippets; I'd like suggestions on how to make this work correctly. TIA.

function checkffDefine (ffDefine) {
var error = "";
if (ffDefine == false) {
	error = "You did not enter an Enhancement Definition.\n";
	}
return error;
}


function checkWholeForm(form) {
    var why = "";
    why += checkffDefine(form.ffDefine.checked);
    if (why != "") {
       alert(why);
       return false;
	   }
return true;
}


FORM NAME="form" ACTION="page2.htm" METHOD="post" onSubmit="return checkWholeForm(this);"

INPUT TYPE="checkbox" NAME="ffDefine" VALUE="ChangeUserInterface"
 Does the user interface need to change?
INPUT TYPE="checkbox" NAME="ffDefine" VALUE="CaptureNewData"
 Is there new data we need to capture?


Keith Purtell, Web/Network Administrator
VantageMed Operations (Kansas City)
Email:  kpurtell(at)vantagemed.com


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