Go4Expert - Inputbox

ok im having trouble with my imput box it crashes when i enter text, nothin and when i press the cancel button. i do realise when i click the cancel buttin it returns a null value and vb doesnt like it but why does it crash with letters or typing nothin because i have put if it = "" then.... shouldnt that mean it will accept nothin entered?

heres one of the input boxes maybe u can tell what im doin wrong and how to fix it.

Code:

If question1 = 1 And level = 0 And x >= 134 And x < 275 Then

            Form1.txtlevel.Text = 1

            x = 134

            aboard.Draw(g)

            Me.Draw(g)



            Dim Q As String

            Dim number1 As Short

            Dim number2 As Short

            Dim result As Short



            number1 = Int((100 * Rnd()) + 1)

            number2 = Int((100 * Rnd()) + 1)

            Q = InputBox("what is " & number1 & " + " & number2 & " ?")

            Randomize()



            result = number1 + number2

            If Q = result Then

                MsgBox("You got it right!")

                question1 = 2

                Form1.Txtquestion1.Text = 2



            ElseIf Q = "" Then

                Form1.Txtlives.Text = Form1.Txtlives.Text - 1

                MsgBox("Correct answer is: " & result & ", Your going back!")

                MsgBox("you Lost of life you have " & Form1.Txtlives.Text & " left")

                x = 134 - 120

                aboard.Draw(g)

                Me.Draw(g)



            Else

                Form1.Txtlives.Text = Form1.Txtlives.Text - 1

                MsgBox("Correct answer is: " & result & ", Your going back!")

                MsgBox("you Lost of life you have " & Form1.Txtlives.Text & " left")

                x = 134 - 120

                aboard.Draw(g)

                Me.Draw(g)

           End if