Ci sono riuscito cosi':

sql4 = "UPDATE t_mrg_pl SET [Panel_71] = IIf(IsNull([Obbligation_1]),'',[Obbligation_1] & Chr(13) & Chr(10)) & IIf(IsNull([Obbligation_2]),'',Chr(13) & Chr(10) & [Obbligation_2] & Chr(13) & Chr(10)) & " & _
"IIf(IsNull([Obbligation_3]),'',Chr(13) & Chr(10) & [Obbligation_3] & Chr(13) & Chr(10)) & IIf(IsNull([Obbligation_4]),'',Chr(13) & Chr(10) & [Obbligation_4]);"

'
Set cmd=CreateObject("adodb.command")
With cmd
Set .ActiveConnection = cn
.CommandType=1 'adCmdText
.CommandText = sql3
.Execute , , 128 '128=adExecuteNoRecords
.CommandText = sql4
.Execute , , 128 '128=adExecuteNoRecords
End With
'
cn.Close
Set cn=nothing