Procedure EditStr(X,Y:Word;MaxLets:Byte;Upper:Boolean;
                      Var MainStr:String);

    This procedure allows the user to  edit  the string MainStr using the
    cursor keys, Insert, Delete, Backspace and ^QY.

    The  string  MainStr  (which  must  have  meaningful  data  in it) is
    displayed  at  X,Y.   EditStr  will  only  allow  the  string  to  be
    MaxLets characters (or less)  in  length.   If  Upper  is set to True
    then EditStr converts all lowercase letters to uppercase letters.

    Cursor  is  automatically  set   True   by   this  procedure  and  it
    restores Cursor to its original value upon exit.