At2()

         Looks for the Nth occurrence in a string

    Syntax:

         At2( cSearch, cTarget [, nOcur] ) -> nPos

         cSearch : The character substring to search for
         cTarget : The character string to search
         nOcur   : Number of the occurrence, default is 1

    Description:

         The parameters are the same as AT() of the standard library
         Clipper.lib except for nOcur that indicates the number of the
         occurrences to return. The default nOcur is 1.
         The function is Case Sensitive.

    Return:

         The same than AT().

    Example:

         ? At2 ( "a", "Manu Roibal" )      //  2
         ? At2 ( "a", "Manu Roibal", 2 )   // 10
         ? At2 ( "a", "Manu RoibAl", 2 )   // 0