meh looking closer there are a few problems, try this:
code:
function OnWndTestEvent_LstBoxSelChanged(PlusWnd,ControlId)
{
if(ControlId == "LstSender")
{
PlusWnd.SetControlText("TxtMessage", PlusWnd.LstBox_GetItemText("LstMessage", PlusWnd.LstBox_GetCurSel("LstSender")));
}
}