上機窗體是在註冊完之後需要上機的時候開始使用，但是具體的一些限制還是需要注意一下，比如該卡
號是否註冊，是否退卡等等，接下來就看看這個過程。
具體程式碼如下所示：

Private Sub cmdOnline_Click()
'定義資料庫物件
Dim mrcStudent As adodb.Recordset
Dim mrcCancelCard As adodb.Recordset
Dim mrcOnline As adodb.Recordset
Dim mrcLine As adodb.Recordset
Dim mrcBasicData As adodb.Recordset

'定義字串語句
Dim OnlineSQL As String
Dim StudentSQL As String
Dim BasicDataSQL As String
Dim LineSQL As String
'定義返回查詢資訊變數
Dim Onmsgtext As String
Dim StuMsgtext As String
Dim BMsgtext As String
Dim LMsgtext As String

'判斷是否輸入卡號
    If Trim(txtCardNo.Text) = "" Then
        MsgBox "請輸入卡號！", 0 + 48, "溫馨提示"
        txtCardNo.SetFocus
        Exit Sub
    Else
        '判斷輸入的是否是數字
        If Not IsNumeric(txtCardNo.Text) Then
            MsgBox "請輸入數字", 0 + 48, "溫馨提示"
            txtCardNo.Text = ""
            txtcard.SetFocus
            Exit Sub
        Else
    '判斷此卡是否存在
        StudentSQL = "select * from student_info where cardno='" & Trim(txtCardNo.Text) & "'"
        Set mrcStudent = ExecuteSQL(StudentSQL, StuMsgtext)
        
    '判斷是否註冊
        If mrcStudent.EOF Then
            MsgBox "此卡尚未註冊！", 0 + 48, "提示"
            txtCardNo.SetFocus
            txtCardNo.Text = ""
            mrcStudent.Close
            Exit Sub
        Else
        '判斷是否退卡
            If mrcStudent.EOF = False And mrcStudent.Fields(10) = "未使用" Then
                MsgBox "該卡號已經退卡，不能上機！", 0 + 48, "警告"
                txtCardNo.Text = ""
                txtCardNo.SetFocus
                mrcStudent.Close
            Else
    
            '判斷餘額是否大於最小上機金額
                If Val(mrcStudent.Fields(7)) < Val(Register.txtRecharge) Then
                    MsgBox "親，餘額不足，請充值！", 0 + 48, "提示"
                    mrcStudent.Close
                    Exit Sub
                Else
                '判斷是否上機
                OnlineSQL = "select * from online_info where cardno='" & txtCardNo.Text & "'"
                Set mrcOnline = ExecuteSQL(OnlineSQL, Onmsgtext)
    
                    If Not mrcOnline.EOF Then
                    MsgBox "此卡正在上機！", 0 + 48, "提示"
                    Exit Sub
                    Else
    
                    '更新上下機介面
                    txtSID.Text = mrcStudent.Fields(1)
                    txtDept.Text = mrcStudent.Fields(4)
                    txtSex.Text = mrcStudent.Fields(3)
                    txtondate.Text = Date
                    txtOntime.Text = Time
                    txttype.Text = mrcStudent.Fields(14)
                    txtName.Text = mrcStudent.Fields(2)
                    txtBalance.Text = mrcstduent.Fields(7) '餘額更新
                      
                    '更新Online表
                    OnlineSQL = "select * from online_info where cardno='" & Trim(txtCardNo.Text) & "'"
                    Set mrcOnline = ExecuteSQL(OnlineSQL, Onmsgtext)
                    
                    mrcOnline.AddNew
                    mrcOnline.Fields(0) = Trim(txtcard.Text)
                    mrcOnline.Fields(1) = Trim(txttype.Text)
                    mrcOnline.Fields(2) = Trim(txtSID.Text)
                    mrcOnline.Fields(3) = Trim(txtName.Text)
                    mrcOnline.Fields(4) = Trim(txtDept.Text)
                    mrcOnline.Fields(5) = Trim(txtSex.Text)
                    mrcOnline.Fields(6) = Trim(txtondate.Text)
                    mrcOnline.Fields(7) = Trim(txtOntime.Text)
    
                    '獲取計算機的名字
                    mrcOnline.Fields(8) = Trim(VBA.Environ("computername"))
                    mrcOnline.Fields(9) = Date
                    
                    mrcOnline.Update
                    mrcOnline.Close
                    
                    '顯示正在上機的人數
                    OnlineSQL = "select * from online_info"
                    Set mrcOnline = ExecuteSQL(OnlineSQL, Onmsgtext)
                    
                        If mrcOnline.EOF = True Then
                            lblPeople.Caption = 0
                        Else
                            lblPeople.Caption = mrcOnline.RecordCount
                        End If
                            label23.Caption = "歡迎光臨"
                        End If
                    End If
                End If
            End If
        End If
    End If
End Sub
 

注意：這個窗體查詢了5個表，所以要定義5個連線資料庫的物件