try this out..
JavaScript part --
var g_selectedCheckboxId = [];
function setLastSelected(checkboxObj) {
if(checkboxObj.checked) {
g_selectedCheckboxId.push(checkboxObj.id);
} else {
g_selectedCheckboxId.splice(g_selectedCheckboxId.indexOf(checkboxObj.id), 1);
}
}
function getLastSelected() {
if(g_selectedCheckboxId.length > 0)
return g_selectedCheckboxId[g_selectedCheckboxId.length-1];
return null;
}
HTML part (assumption) Add onclick event to each and every checkbox -
<input type="checkbox" id="ctl00_ContentPlaceHolder1_cblcheckbox_0" onclick="setLastSelected(this)">Checkbox 1
<input type="checkbox" id="ctl00_ContentPlaceHolder1_cblcheckbox_1" onclick="setLastSelected(this)">Checkbox 2
<input type="checkbox" id="ctl00_ContentPlaceHolder1_cblcheckbox_2" onclick="setLastSelected(this)">Checkbox 3
<input type="checkbox" id="ctl00_ContentPlaceHolder1_cblcheckbox_3" onclick="setLastSelected(this)">Checkbox 4
</br></br></br></br></script>
Regards,
Niral Soni