Dealing with duplicate values

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.NET3.5

.NET

Hi, in my application i am inserting 15 different user details to the DB, the form looks like an excel sheet, i am able to handle duplicate key violation error, and to that i am doing the following

Private Sub btnSubmit_CrtMul_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSubmit_CrtMul.Click
        Dim cnt As Integer = 0
        Try
            If chkBox1_Crtusr.Checked And IsNumeric(txtEmpID_1.Text) Then
                rtrnQry(txtUsrNm_1.Text, txtPswd_1.Text, txtFName_1.Text, txtLName_1.Text, txtEmpID_1.Text, cmbProNm1.SelectedItem, cmbAdmin1.SelectedItem, 1)
                If empIdSts(txtEmpID_1) = True Then
                    Call ClearData(1)
                    cnt = cnt + 1
                End If
            ElseIf Not IsNumeric(txtEmpID_1.Text) And txtEmpID_1.TextLength > 0 Then
           Call isNumSts(lblsts1, chkBox1_Crtusr)
            End If
If chkBox2_Crtusr.Checked And IsNumeric(txtEmpID_2.Text) Then rtrnQry(txtUsrNm_2.Text, txtPswd_2.Text, txtFName_2.Text,txtLName_2.Text, txtEmpID_2.Text,cmbProNm2.SelectedItem, cmbAdmin2.SelectedItem, 2)
If empIdSts(txtEmpID_2) = True Then
      Call ClearData(2)
      cnt = cnt + 1
End If
ElseIf Not IsNumeric(txtEmpID_2.Text) And txtEmpID_2.TextLength > 0 Then
Call isNumSts(lblsts2, chkBox2_Crtusr)
End If

I am doing this for all 15 users, using the following code i m handing duplicate key value

Public Sub chkEmpIDSts(ByVal txtbox As TextBox, ByVal lblSts As Label, ByVal chkBox As CheckBox)
       Try
           Dim empIDLngth As String = ""
           Using conn As New SqlConnection(sqlConnStr)
               conn.Open()
               Using cmd As New SqlCommand("rtnLngth", conn)
                   With cmd
                       .CommandType = CommandType.StoredProcedure
                       .Parameters.AddWithValue("@empid", txtbox.Text)
                       empIDLngth = .ExecuteScalar()
                   End With
                   If txtbox.TextLength > 0 Then
                       If empIDLngth = 0 Then
                           lblSts.Text = "Available"
                           lblSts.ForeColor = Color.LimeGreen
                           If chkBox.Enabled = False Then chkBox.Enabled = True
                       Else

                           lblSts.Text = "Not available"
                           lblSts.ForeColor = Color.Red
                           If chkBox.Checked Then
                               chkBox.CheckState = CheckState.Unchecked
                               chkBox.Enabled = False
                           End If

Every thing is going good till now, but my question is,if some one enters the same new empId twice for two different user, than my code wont be able to handle it as it checks if the empid is already thr in DB, and user will be able to insert it - hence will again get a duplicate key violation error. Please post me an idea to resolve the problem.Thanks