How to make Random

Maybe this?

Public Class Form1

    Dim Test As Integer = 0

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Timer1.Interval = 7
    End Sub

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Timer1.Start()
    End Sub

    Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
        Dim Test As Integer = CInt(DateTime.Now.Millisecond.ToString) - 1
        If Test = -1 Then
            Button1.BackColor = Color.Red
            Button1.Text = "Waiting"
        Else
            Button1.BackColor = Color.Lime
            Button1.Text = Test.ToString
            Timer1.Stop()
        End If
        Timer1.Interval = Math.Round(System.Math.Sqrt(Test))
        Me.Text = Timer1.Interval.ToString
    End Sub

End Class

You've taught me everything I know but not everything you know.