Getting Form Details With A Function

Is there a way to access a forms details by sending its parameters to a
function. For example, I have a form named "myForm" populated by a drop down box, so that <select name="mySel">

I am trying to send the form and drop down box name to a javascript
function, eg onChange="update( "myForm", "mySel") so that, within the Javascript update(formName, selName) function I can access the forms doing something like this:

update(formName, selName)
{
selected_index = document.forms.formName.selectedIndex;
selected_value = document.forms.formName.selName[selectedIndex];
}

so that I can access the specified value using the input arguments to
the function, rather than doing

selected_index = document.forms.myForm.selectedIndex;
selected_value = document.forms.myFormn.mySel[selectedIndex];

The reason for this is because I have a lot of drop box boxes that are
changed by the user.