在excel中更新Access表中的脱审年限

我想通过以下代码从excel中更新Access表中的“脱审年限”字段的值，但提示：update语句的语法错误!
特向高手求救！
Public Sub 更新脱审年限()
    Dim mydata As String, mytable As String, SQL As String
    Dim cnn As ADODB.Connection
    Dim rs As ADODB.Recordset
    mydata = ThisWorkbook.Path & "\myDATA.mdb"
    mytable = "发卡数据库"
    Set cnn = New ADODB.Connection
    With cnn
        .Provider = "microsoft.jet.oledb.4.0"
        .Open mydata
    End With
    SQL = "update " & mytable _
        & " set 脱审时间=year(now())-year(最新合格日期)," '_
       Set rs = cnn.Execute(SQL)
    MsgBox "已经成功更新了脱审年限！", vbInformation + vbOKOnly
    cnn.Close
    Set rs = Nothing
    Set cnn = Nothing
End Sub

在线等待，呼叫高手帮忙！！！！！！