ถ้า AutoID ผมเก็บจนถึง ID สุดท้าย จะให้แจ้งเตือนความ "ความจุเต็ม" ต้องกำหนดยังไงครับ

If IsDBNull(Count) = True Then
txtRM_AddID.Text = "RM" & "000" & iMAX
Else If iMAX< ค่า ความจุเต็ม Then
iMAX = Count + 1
Else 
"ค่า ความจุเต็ม"
End If

intNum = "RM" & iMAX

intNum = iMAX.ToString("RM0000")

If iMAX <= 9 Then
intNum = "RM" & "000" & iMAX
ElseIf iMAX <= 99 Then
intNum = "RM" & "00" & iMAX
ElseIf iMAX <= 999 Then
intNum = "RM" & "0" & iMAX
ElseIf iMAX <= 9999 Then
intNum = "RM" & iMAX
End If

intNum = iMAX.ToString("RM0000")

If iMAX <= 9 Then
intNum = "RM" & "000" & iMAX
ElseIf iMAX <= 99 Then
intNum = "RM" & "00" & iMAX
ElseIf iMAX <= 999 Then
intNum = "RM" & "0" & iMAX
ElseIf iMAX <= 9999 Then
intNum = "RM" & iMAX
End If

If IsDBNull(Count) = True Then
txtRM_AddID.Text = "RM" & "000" & iMAX
Else If iMAX< 9999 Then
iMAX = Count + 1
Else 
"ค่า ความจุเต็ม"
End If

If IsDBNull(Count) = True Then
txtRM_AddID.Text = "RM" & "000" & iMAX
ElseIf iMAX <= 9999 Then
iMAX = Count + 1
Else
lblMsg.Text = "ค่า ความจุเต็ม"
'ก็ต้องออกไปด้วยครับ จะ exit sun , close ,return หรืออะไรก็ว่ากันไป
'สรุป คือ คุณหยุดแค่นี้นะเพราะมันเกิน 9999 ไปแล้วประมาณนี้ครับ
End If

Function SQLExecute(_sql As String) As Integer
        Dim objConn As SqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("con").ConnectionString())
        objConn.Open()
        Dim objCmd As SqlCommand = New SqlCommand(strSQL, objConn)
        Dim Count As Integer= objCmd.ExecuteScalar()
        objConn.Close()
    End Function

    Private Sub AddAutoID()
        Dim Count As Integer = SQLExecute("SELECT MAX(RIGHT(RM_ID,4)) AS RM_ID FROM RawMaterial_New")
        Dim iMAX As Integer = IIf(Count <= 0, 1, Count + 1)
        If iMAX < 10000 Then
            If SQLExecute(strSQL = "INSERT INTO RawMaterial_New (RM_ID) VALUES ('" & (IIf(Count <= 0, 1, Count + 1)).ToString("RM0000") & "')") > 0 Then
                MsgBox("บันทึกสำเร็จ")
            Else
                MsgBox("บันทึกไม่สำเร็จ เศร้าใจสิ้นดี")
            End If

        Else
            MsgBox("มันเกิน 9999 ไปแล้วนะ")
        End If

    End Sub

Imports System.Data.SqlClient

Public Class Manage_RawMaterial_New
    Inherits System.Web.UI.Page

    Dim objConn As SqlConnection
    Dim objCmd As SqlCommand
    Dim strConnString, strSQL As String

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    End Sub

    Public Sub ConnectDB()

        strConnString = ConfigurationManager.ConnectionStrings("con").ConnectionString
        objConn = New SqlConnection(strConnString)

    End Sub

    Private Sub AddAutoID()

        Dim intNum As String = Nothing
        Dim Count As Integer

        ConnectDB()

        strSQL = "SELECT MAX(RIGHT(RM_ID,4)) AS RM_ID FROM RawMaterial_New"
        objCmd = New SqlCommand(strSQL, objConn)

        objConn.Open()
        Count = objCmd.ExecuteScalar()
        objConn.Close()

        Dim iMAX As Integer = IIf(Count <= 0, 1, Count + 1)

        If iMAX < 10000 Then
            Dim result As Integer

            strSQL = "INSERT INTO RawMaterial_New (RM_ID) VALUES ('" & iMAX.ToString("RM0000") & "')"
            objCmd = New SqlCommand(strSQL, objConn)

            objConn.Open()
            result = objCmd.ExecuteNonQuery()
            objConn.Close()

            MsgBox("บันทึกสำเร็จ")
        Else
            MsgBox("ข้อมูลเต็ม")
        End If

    End Sub

    Protected Sub btnRM_Add_Click(sender As Object, e As EventArgs) Handles btnRM_Add.Click

        AddAutoID()

    End Sub

End Class