XPnextStr()
  Useful string function for a SEEK of the last occurence
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   Function:   XPnextStr()

               This function could be used as a replacement of the
               following statement:

                 seek Left(cString,Len(cString) - 1) +;
                      Chr(Asc(Right(cString,1)) + 1)

               where the following could be used:

                 seek XPnextStr(cString)

               XPnextStr() just add's to the last character of
               a string, so that a SEEK (with SoftSeek On),
               seek's the next index expression in the database,
               where the index is not fixed. Skip -1 then is for
               instance the last occurence of that key field.

               There is one case where this function does not
               work; that is when the last character of the string
               eXPression is chr(255).

   Syntax:     XPnextStr(cString) --> cNextString

   Arguments:  <cString> is the string (key value), to search the
               next occurence of, in Non unique key expressions.

   Returns:    <cNextString> is the next "possible" string of cString.

   Usage:      seek XPnextStr(cKey)
               skip -1
               * - Now on last occurence.