I have a next.gif that when clicked should go a java script function in an included file

in particular in a page i have,

<A HREF="#" onclick="jumpto(mainform, this, 1, <%=maxSections%>; return false;"><img border=0 src="images/arrw01_01a.gif"></A>

and i have

<script Language="JavaScript"><!--

function jumpto(f, theField, theValue, maxSection)
{
var thesection = 0;

//var index;
if (theValue == 0)
{
index = theField.selectedIndex;
thesection = theField[index].value;
}
if (theValue == -1)
thesection = parseInt(f.whichsection.value,10) - 1;
if (theValue == 1)
thesection = parseInt(f.whichsection.value,10) + 1;
// if (thesection > maxSection)
// thesection = maxSection;
// if (thesection == 0)
// thesection = 1;
f.whichsection.value = thesection;
alert("In the js");
f.submit();
//return (false);

}

//--></script>


it is not updating the "whichsection" hidden field. so the question is why it isn't working and what is the proper use of "this".