RadioButto(<nRow>, <nColumn>, [<cCaption>])
        --> oRadioButto

 Arguments

     <nRow> is a numeric value that indicates the screen row of the radio
     button.

     <nColumn> is a numeric value that indicates the screen column of the
     radio button.

     <cCaption> is an optional character string that contains a text
     string that describes the radio button on the screen.  The default is an
     empty string.

 Returns

     Returns a RadioButto object when all of the required arguments are
     present; otherwise, RadioButto() returns NIL.