Validate Element

I have a script that works:

function element_exists(element_name) {
if(document.getElementsByName(element_name).length > 0) {
return true;
} else {
alert("Please make sure the Title field was properly completed.");
return false;
}}

The only problem is that I need it to return false only if one of the form radios ('useit') is checked to "no". I was trying something like this

function element_exists(element_name) {
var checkuse = document.getElementsById(useit).value;

if(checkuse=="no" || !checkuse) {
if(document.getElementsByName(element_name).length > 2) {
return true;
} else {
alert("Please make sure the Title field was properly completed.");
return false;
}
} else {
return true;
}}

If you are wondering why I have !checkuse, it is because the form is dynamically created and sometimes does not even include the element 'useit'. How can I do this. If radio 'useit' checked to "no" or doesn't exist, run the function.