Function PosFrom(SubS:String;StIn:String;FarIn:Byte):Byte;

    Similar to the Pos  function  in  Pascal.   It  searches  for SubS in
    StIn and returns  0  if  not  found,  otherwise  the  offset  of  the
    first letter.  The difference is  it  does not always search from the
    beginning of  the  string,  it  searches  from  a  certain  character
    onwards.

    Examples

    Pos(SubS,StIn) = PosFrom(SubS,StIn,1);

    Pos('A','ABCABC') = 1

    PosFrom('A','ABCABC',2) = 4