Looking for a better way to evaluate textbox controls

I have multiple textboxes that should have numeric values and others that need to have some kind of entry added. So far I have been doing it this way but I am wondering if there is a better way. How would you do this?

VB Code:

Dim strAction As String = txtAction.Text
        Select Case strAction
            Case "A"
                If IsNumeric(txtEmp.Text) = False Then
                    MsgBox("Employee number must be a numeric value.", _
                          MsgBoxStyle.OKOnly, "Employee Number Error")
                    txtEmp.Focus()
                    Exit Sub
                End If
                If IsNumeric(txtDayCode.Text) = False Then
                    MsgBox("This field must be a numeric value 1-7.", _
                        MsgBoxStyle.OKOnly, "Day Code Error")
                    txtDayCode.Focus()
                    Exit Sub
                End If
                If (txtJobNumber.Text) = "" Then
                    MsgBox("The job number field can not be left blank.")
                    txtJobNumber.Focus()
                    Exit Sub
                End If
                If (txtPC.Text) = "" Then
                    MsgBox("The Pc Field can not be left blank.")
                    txtPC.Focus()
                    Exit Sub
                End If
                If (txtTime.Text) = "" Then
                    MsgBox("The time field can not be left blank.")
                    txtTime.Focus()
                    Exit Sub
                End If
                If (txtAmount.Text) = "" Then
                    MsgBox("The amount field can not be left blank.")
                    txtAmount.Focus()
                    Exit Sub
                End If

You could try adding the type of validation to the tag property and then just loop through the textboxes on the form ie
For those that must be numeric add numeric to the tag property and those that can not be blank add noNull to the tag property then just loop through like so

VB Code:

For Each ctl As Control In Me.Controls
            If TypeOf ctl Is TextBox Then
                Dim tBox As TextBox = DirectCast(ctl, TextBox)
                Select Case tBox.Tag
                    Case "numeric"
                        Dim intTest As Integer
                        If Not Integer.TryParse(tBox.Text, intTest) Then
                            MessageBox.Show(tBox.Name & " must be numeric")
                            tBox.Focus()
                        End If
                    Case "noNull"
                        If tBox.Text = String.Empty Then
                            MessageBox.Show(tBox.Name & " can not be null")
                            tBox.Focus()
                        End If
                End Select
            End If
        Next

or another example is if you want custom error messages, put the error message in the tag property but start the line with an identifier for type like so
txtEmp.Tag = "N*Employee number must be a numeric value."
txtJobNumber.Tag = "R*"The job number field can not be left blank."

where N* signifies a numeric field and R* signifies required (just examples, you could use whatever you want)

VB Code:

For Each ctl As Control In Me.Controls
            If TypeOf ctl Is TextBox Then
                Dim tBox As TextBox = DirectCast(ctl, TextBox)
                Dim type As String = tBox.Tag.ToString.Substring(0, 2)
                Select Case type
                    Case "N*"
                        Dim intTest As Integer
                        If Not Integer.TryParse(tBox.Text, intTest) Then
                            MessageBox.Show(tBox.Tag.ToString.Replace(type, String.Empty))
                            tBox.Focus()
                        End If
                    Case "R*"
                        If tBox.Text = String.Empty Then
                            MessageBox.Show(tBox.Tag.ToString.Replace(type, String.Empty))
                            tBox.Focus()
                        End If
                End Select
            End If
        Next