js code:
>>>function OnWndMenuEvent_CtrlClicked(Wnd, ControlId)<<<
{
if(ControlId == "BtnLetters")
{
>>> Wnd = MsgPlus.CreateWnd("Letters.xml", "WndLetters");<<<
}
}
You are using Wnd twice that isn't the problem but that is a no no.
Does the window open at all? If not what shows in the debug window?