Private Sub Form_Load()
    Dim rs As Object
    sql = "select * from 车辆档案 "
    connstr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\VB数据\db1.mdb;Persist Security Info=False"
      Set rs = CreateObject("ADODB.Recordset")
              'strRS = "select ID,Use_Name,Use_tel,Address,ClientName,Use_mem from KHtable  order by ID DESC"
    sql = "select * from 车辆档案"
    rs.Open strRS, conn, 0, 1
   
    If Adodc2.Recordset.RecordCount = 0 Then Exit Sub
    For i = 0 To Adodc2.Recordset.RecordCount - 1
        Combo1.AddItem Adodc2.Recordset.Fields(0).Value
        Adodc2.Recordset.MoveNext
    Next
   
    Adodc3.RecordSource = "select * from 车辆档案"
    Adodc3.Refresh
   
    If Adodc3.Recordset.RecordCount = 0 Then Exit Sub
    For i = 0 To Adodc3.Recordset.RecordCount - 1
        Combo2.AddItem Adodc3.Recordset.Fields(0).Value
        Adodc3.Recordset.MoveNext
    Next
    On Error Resume Next
    Combo1.Text = Adodc1.Recordset.Fields(1)
    Combo2.Text = Adodc1.Recordset.Fields(2)
End Sub

Dim sql As String
Combo1.Clear
sql = "select * from 车辆档案"
rs.Open sql, connstr, 3, 3
Do While Not rs.EOF
    Combo1.AddItem rs.field(0)
    rs.MoveNext
Loop
rs.Close

放在combo1的gotfocus方法下