怎么实现VB和SQL Server连接啊？

我的数据库的信息
1.服务器名是ALLEN， 2。 登陆名是sa， 3.登陆密码为空
我的一个界面的代码如下
登陆界面代码
Private Declare Function GetUserName Lib "advapi32.dll" Alias "GetUserNameA" (ByVal lpbuffer As String, nSize As Long) As Long

Public OK As Boolean
'记录确定次数
Dim miCount As Integer
Private Sub Form_Load()
Dim sBuffer As String
Dim lSize As Long

sBuffer = Space$(255)
lSize = Len(sBuffer)
Call GetUserName(sBuffer, lSize)
If lSize > 0 Then
txtUserName.Text = ""
Else
txtUserName.Text = vbNullString
End If
End Sub

Private Sub cmdCancel_Click()
OK = False
Me.Hide
End Sub

Private Sub cmdOK_Click()
Dim txtSQL As String
Dim mrc As ADODB.Recordset
Dim MsgText As String
'ToDo: create test for correct password
'check for correct password

UserName = ""
If Trim(txtUserName.Text = "") Then
M

连接数据库简单的登录 代码如下
Dim conn As ADODB.Connection
Dim rs As ADODB.Recordset
Dim loginflag As Boolean

Private Sub Command1_Click()
Set conn = New ADODB.Connection
Set rs = New ADODB.Recordset
'建立无源数据库连接
conn.ConnectionString = "driver={sql server};server=12-3FDA18CE0DDC;uid=sa;pwd=sa;Database=test"
conn.ConnectionTimeout = 50
conn.Open
Dim str As String
'连接连接对象
Set rs.ActiveConnection = conn
'设置游标类型
rs.CursorType = adOpenDynamic
If Trim(Text1.Text = "") Then
MsgBox "用户名不能为空，请重新输入用户名！", vbOKOnly + vbExclamation, "警告"
Text1.SetFocus
Else
'设置查询字符串
str = "select * from tt where name ='" & Trim(Text1.Text) & "'"
rs.Open str
If rs.EOF = True Then
MsgBox "没有这个用户，请重新输入用户名!", vbOKOnly + vbExclamation, "警告"
Text1.SetFocus
Else
'登录成功，连接主窗口