VB6.0编写系统登录代码时遇到“实时异常3021”

VB6.0编写系统登录代码时遇到“实时错误3021”
请各位高手帮我一下，这段代码要怎么改，详细点，谢谢！
Option Explicit
Public conn As New ADODB.Connection
Public Userid As String
Dim cs As Integer '登录次数
Dim pwd As String
Dim rsUser As ADODB.Recordset

Private Sub Combo1_Click()
Dim sql As String
Set rsUser = New ADODB.Recordset
If rsUser.State = 1 Then rsUser.Close
sql = "select Userpwd from Userinfo where Userid='combo1.text'"
rsUser.Open sql, conn, adOpenStatic, adLockPessimistic
Text1.SetFocus
pwd = Trim(rsUser.Fields("Userpwd"))
调试时，这句标记为黄色！
End Sub

Private Sub Command1_Click()
If Combo1.Text = "" Then
MsgBox "请选择用户名！", , "登录"
Combo1.SetFocus
Exit Sub
End If
If Text1.Text = "" Then
MsgBox "请输入密码！", , "登录"
Text1.SetFocus
Exit Sub
End If
If Text1.Text = pwd Then
Userid = Combo1.Text
Me.Hide
Form2.Show
Else
MsgBox "密码无效，请重试！", , "登录"
Text1.SetFocus
cs = cs + 1
If cs = 3 Then
Unload Me
End If
End If
End Sub

Private Sub Form_Load()
Dim sql As String
Set rsUser = New ADODB.Recordset
conn.ConnectionString = "provider=Microsoft.jet.oledb.4.0;data source=human resource.mdb"
conn.Open
sql = "select Userid from Userinfo"
rsUser.Open sql, conn, adOpenDynamic, adLockPessimistic
Combo1.Clear
Do Until rsUser.EOF
Combo1.AddItem rsUser.Fields("Userid")
rsUser.MoveNext
Loop
cs = 0
End Sub


[解决办法]

VB code

sql = "select Userpwd from Userinfo where Userid='"& combo1.text &"'"rsUser.Open sql, conn, adOpenStatic, adLockPessimisticif rsUser.recordcount>0 then    Text1.SetFocus    if not isnull(rsUser.fields("Userpwd")) then        pwd = Trim(rsUser.Fields("Userpwd"))    end ifend if