1st way:
If TextBox1.Text >0 and TextBox1.Text< 14 Then
Textbox2.Text = 1
Else If Textbox1.Text>15 and TextBox1.Text< 29 Then
Textbox2.Text = 2
Else
Textbox2.Text = 3
End If
2nd way:
Select TextBox1.text
case >0 and <14
TextBox2.text=1
case >15 and <29
TextBox2.Text=2
Case >= 30
TextBox2.text=3
End select