PushButton(<nRow>, <nColumn>, [<cCaption>])
        --> oPushButton

 Arguments

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

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

     <cCaption> is an optional character string that describes the push
     button on the screen.  If omitted, the default is an empty string.

 Returns

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