Okay, after looking and and searching, I now have:

```
Dim num As Integer
Dim i As Integer
Dim counter As Integer
num = TextBox1.Text
counter = 0
i = 1
Do While i <= num
If num Mod i = 0 Then
counter = counter + 1
End If
i = i + 1
Loop
If counter = 2 Then
TextBox2.Text = "This is a prime number!"
Else
TextBox2.Text = "This is NOT a Prime number!"
End If
```

However, I don't know what the counter does exactly.. (part of this was copied)

Could someone explain?