>I can build a form with an olebject referring to msChart20 but i don't know how to manage it.

It's so easy.
I adapted my codes as a sample.
taken your oleobject name as "graph":

#DEFINE crlf		CHR(13)+CHR(10)
#DEFINE tab 		CHR(9)

	CREATE CURSOR graph (graph g)
	APPEND BLANK
	nomsgraph=.f.
	ON ERROR nomsgraph=.t.
	APPEND GENERAL graph CLASS "msgraph.chart"
	 ON ERROR 
	 IF nomsgraph
            messagebox("no ms-graph found!..")
	         RETURN .f.
	 ENDIF 
	
cdata=""

SELECT sales

  SCAN
     cdata=m.cdata+tab+month_name
  ENDSCAN 
     cdata=cdata+crlf+"Month"

  SCAN 
     cdata=cdata+tab+trans(amount)
  ENDSCAN 

     SELECT graph 
    APPEND GENERAL graph DATA m.cData
	thisform.graph.ControlSource="graph.graph"


thisform.graph.hastitle=.t.
thisform.graph.ChartTitle.Caption=" Sales "

*thisform.graph.Legend.Shadow=.t.

Note: Maybe I did some syntax mistakes when summarising... Should be care for mistakes...