I want to make a random function here, so when i press Button3 it's gonna replace the number "star.**9902**" to a completely new random number, Without replace the text "**star.**" and then show up in Textbox1.
But right now everything is getting replaced including the text.

I'm pretty new to coding so it would be great if you guys can help me out.
vb13.

```
Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click

    If TextBox1.Text.Contains("star.9902") Then
        TextBox1.Text = TextBox1.Text.Replace("star.9902", "star. 'Here goes the random numbers")

    End If
    Dim rand As New Random

    Dim letter As String = ""

    For i = 0 To 3

        letter = letter & ChrW(rand.Next(Asc("0"), Asc("9") + 1))

    Next

    TextBox1.Text = letter

End Sub

```