程序代码：

Dim cn As New ADODB.Connection
Private Sub Command1_Click()
Dim sql As Variant
Set rs = New ADODB.Recordset
sql = "select * from user where  username=" & Text1.Text & ""
rs.Open sql, cn, 1, 1
If rs.EOF = True Then
  MsgBox "该用户名不存在", vbOKCancel + 48, "提示"
  Else
  If rs("userpassword") = Trim(Text2.Text) Then
  main.Show
  Unload Me
  Else
   MsgBox "密码输入错误", vbOKCancel + 48, "错误"
   Text2.Text = ""
   Text2.SetFocus
   End If
End If
   
   
End Sub

Private Sub Form_Load()

Set cn = New ADODB.Connection
cn.Open "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & App.Path & "\file.mdb;Persist Security Info=False"
Dim rs As ADODB.Recordset
End Sub