Now I am able to read and write from and to cells of Excel unicode characters

In this way
This a little program that read from the first record of a dbf table that contains in one field some chinese characters
and create a excel sheet write into cells
Then read from these cells and append a record into dbf table and populate the fields with the values of the cells

Many thanks to Mr Rao and Fwh support!

include "fivewin.ch"

FUNCTION Main()

local oExcel, oBook, oSheet, oWnd, oClp
local nRow, nCol, nCols, uVal, uVal2

FW_SetUnicode( .t. )

DEFINE WINDOW oWnd
oClp := TClipboard():New()

USE "AA_CHN"
GO TOP
nCols := FCount()

oExcel := ExcelObj()
oBook := oExcel:WorkBooks:Add()
oSheet := oBook:ActiveSheet

uVal := FieldGet( 1 )
scrivicella( "A1" , uVal , oSheet , oClp )

uVal := FieldGet( 2 )
scrivicella( "B1" , uVal , oSheet , oClp )

uVal := FieldGet( 3 )
scrivicella( "C1" , uVal , oSheet , oClp )

oExcel:Visible := .T.
APPEND BLANK
fieldput( 1 , leggicella( "A1" , oSheet , oClp , oExcel ) )
fieldput( 2 , leggicella( "B1" , oSheet , oClp , oExcel ) )
fieldput( 3 , leggicella( "C1" , oSheet , oClp , oExcel ) )

oClp:End()
oWnd:End()

return nil

FUNCTION LEGGICELLA( cRange , oAs, oClp ,oExcel )
LOCAL cRitorna

oAs:Range( cRange ):Select()
oExcel:Selection:Copy()
cRitorna := oClp:GetUnicodeText()

RETURN cRitorna

FUNCTION SCRIVICELLA( cRange , uVal , oAs, oClp )
LOCAL uVal2 := TRIM( uVal )

IF ValType( uVal ) == 'C' .AND. IsUtf8( uVal2 )
oClp:SetText( uVal2 )
oAs:Range( cRange ):Select()
oAs:Paste()
oClp:Clear()
ELSE
oAs:Range( cRange ):Value := uVal2
ENDIF

RETURN NIL