update 日期字段时出错？

Private Sub 追加_Click()
    Dim rsE As New ADODB.Recordset
    Dim ssql As String
    Dim i As Integer, m1 As Integer, m2 As Integer
     ssql = "SELECT * FROM 签单及收款进度导入表 AS a WHERE [id] = (select  max([id]) from 签单及收款进度导入表 b where  a.合同编号=b.合同编号)"
    rsE.Open ssql, CurrentProject.Connection, adOpenKeyset, adLockOptimistic
    m1 = 0: m2 = 0
    For i = 1 To rsE.RecordCount
        If DCount("合同编号", "签单及收款进度表", "合同编号='" & rsE!合同编号.Value & "'") > 0 Then
           ' If DLookup("收尾款时间", "签单及收款进度表", "合同编号='" & rsE!合同编号.Value & "'") < rsE!收尾款时间.Value Then
                ssql = "update 签单及收款进度表 set 收尾款时间=#" & rsE!收尾款时间.Value & "#,"
                ssql = ssql & "首付款=" & rsE!首付款.Value & ","
                ssql = ssql & "二期款=" & rsE!二期款.Value
                ssql = ssql & " where 合同编号='" & rsE!合同编号.Value & "'"
                CurrentDb.Execute ssql
                m1 = m1 + 1
          ' End If
        Else
            ssql = "insert into 签单及收款进度表 (合同编号,收首期款时间,收二期款时间,收三期款时间,收尾款时间,首付款) "
            ssql = ssql & "values ('" & rsE!合同编号.Value & "',#"
            ssql = ssql & rsE!收首期款时间.Value & "#,#"
            ssql = ssql & rsE!收二期款时间.Value & "#,#"
            ssql = ssql & rsE!收三期款时间.Value & "#,#"
            ssql = ssql & rsE!收尾款时间.Value & "#,"
            ssql = ssql & rsE!首付款.Value & ")"
            CurrentDb.Execute ssql
            m2 = m2 + 1
        End If
        rsE.MoveNext
    Next
    rsE.Close: Set rsE = Nothing
    Me.签单及收款进度表.Requery
    MsgBox "修改首付款记录数：" & m1 & Chr(13) & Chr(10) & "追加新纪录数：" & m2
End Sub

问题：如果加上“If DLookup("收尾款时间", "签单及收款进度表", "合同编号='" & rsE!合同编号.Value & "'") < rsE!收尾款时间.Value Then。。。endif  能运行，但取消这二行，就提示”运行错误3144 ，update语句的语法错误“，请问问题在哪？