You've to convert THISFORM.ddebut and THISFORM.dfin to proper date literals. Something like

? "^{" + TRANSFORM(DTOS(DATE()), "@R 9999/99/99") + "}"

>
>Sorry a little mistake.
>
>

>TEXT To lcSql NOSHOW TEXTMERGE
>SELEC T.Cnomteleph , T.iid FROM ;
>Employee AS 'E' INNER JOIN TELEPH AS 'T' ON E.iTelephoneid = T.iid ;
>    INNER JOIN Horaire AS 'H' ON E.iid = H.iEmployeeId ;
>    WHERE H.ddate BETW  <<THISFORM.ddebut>> AND <<THISFORM.dfin>>  ;
>    GROUP BY 1 , 2 INTO ARRAY taSelectedList
>  ENDTEXT
>
>  =EXECSCRIPT( lcSql )
>
>

>
>I have a strange error "Operator/operand type mismatch. " ( perhaps thisform.ddebut ? )
>
>What can i do ?
>
>thank in advance
>
>bernhart