Here's a snippet from a web project that Jake was lucky enough to inherit ...

Private Sub btnRun_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) 
        Dim QnumAs2 As Int16 = Server.HtmlEncode(Request.Cookies("QnumAs").Value)
        lblError.Visible = False
        If answer1.Text = "" Or answer2.Text = "" Then
            Beep()
            lblError.Text = "ERROR: Answers can NOT be BLANK!!!"
            lblError.Visible = True
            Exit Sub
        End If

        If (QnumAs2 > 2 And answer3.Text = "") Or (QnumAs2 > 3 And answer4.Text = "") Or _
           (QnumAs2 > 4 And answer5.Text = "") Then
            Beep()
            lblError.Text = "ERROR: Answers can NOT be BLANK!!!"
            lblError.Visible = True
            Exit Sub
        End If

In case you're not versed in ASP.NET, this is server side code, executed on the web-server ... hey, atleast the network admin will know when you input a blank answer!