Confirm Field Selected in Multi-Update during Row_Updating

Is there a way to check if a field was checked to be updated in the Row_Updating event

if(CurrentPageID() == “update”){
if(field selected){
$rsnew[‘field’] = some value;
}else{
$rsnew[‘field’] = some other value;
}
}

The checkboxes are named “u_fieldname”, you may get the value by $_POST.