Rendering cfgrid through js

Question

i have a html cfgrid that should be populated by a cfc
to the cfc i'm passing 4 column names and a string (as form field values)
this works fine with a cfinvoke, when page loads first. but now i want to be able to pass different values to cfc and reload my grid with the new values.
i've created a proxy <cfajaxproxy cfc="repfunc" jsclassname="rproxy" />
created a js function:
function srcCxReqs(srcReqs,f1,f2,f3,f4) {
         var instance = new rproxy();
         instance.srcCxReqs(srcReqs,f1,f2,f3,f4);
         ColdFusion.Grid.refresh('testgrid');
created a button that collects (correctly) the values to pass and calls the js function:
<button name="getReqs" onClick="srcCxReqs(getElementById('srcReqs').value, getElementById('f1').options[f1.selectedIndex].value, getElementById('f2').options[f2.selectedIndex].value, getElementById('f3').options[f3.selectedIndex].value, getElementById('f4').options[f4.selectedIndex].value)">
<cfgrid name="testgrid" format="html" query="cxReqs"></cfgrid>
but when i try it, get "Exception thrown and not caught, cfajax.js, Code:0
i'm not even sure the cfajaxproxy is the right way to do it.
does anybody have a working example of a cfgrid being renedered again by a js function?
thanks

Answer 1

getting desperate, at this point i would settle even for "how to reload a cfgrid by clicking on a button"
even this throws an "object does not support this property or method"
<cfajaxproxy cfc="repfunc" jsclassname="rproxy" />
function refreshGrid() {
        var instance = new rproxy();
        myGrid=ColdFusion.getGridObject('testgrid');
        myGrid.getStore();
        ColdFusion.Grid.refresh('testgrid');
<input type="button" name="getReqs" value="Refresh"  onClick="refreshGrid()">
<cfgrid name="testgrid" format="html" query="cxReqs"></cfgrid>
thanks for any help