I try this but it's opening an empy Report
Dim chaine as string
param1 = #1/1/2018#
param2 = #1/31/2018#
DoCmd.OpenReport "Etat", acViewReport, , , , "D1=" & param1 & "|" & "D2=" & param2
chaine = Reports!Etat.OpenArgs
Print.Debug chaine
in the immediate window the result...