>I have a javascript function. In it, I am receiving an ID. This is between 1 and 50. The function has to be generic and capable of establishing a reference to one of the 50 select HTML controls which exists on the form. One of the goal is to be able to disable or enable the control based on the ID received as a parameter. Anyone has done that before?

From your description of the problem (and assuming the parameter passed in is the Id of the control) all you would need would be:

function changeControl(theId){
document.getElementById(theId).disabled = true;
//etc.
}

so I assume I have not understood the question correctly ?