You will want to use the ComboBox_SelectedIndexChanged() event to capture that the combo box item has been changed. At that point, you will need to check to see which combo box item has been selected and make a decision as to whether the TextBox should be enabled or not. Here is an example. Note: This example assumes that "Alive" is the first item in your combobox at the 0 index.
Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
If ComboBox1.SelectedIndex = 0 Then 'Alive
TextBox1.Enabled = True
Else
TextBox1.Enabled = False
End If
End Sub
Dynamically generate the combobox and add handler.
Dim cmb as New ComboBox
AddHandler cmb.SelectedIndexChanged, AddressOf ComboBox1_SelectedIndexChanged
Me.Controls.Add(cmb)