You could use code like the following to populate a 'StrOut' variable, which is then used to update the document's bookmark (for which I've already provided demo code):
Code:
Private Sub cmdOK_Click()
Application.ScreenUpdating = False
Dim StrOut As String
Select Case cboName.Value
Case "Bob": StrOut = "1"
Case "Cindy": StrOut = "2"
Case "Peter": StrOut = "3"
Case "Vanessa": StrOut = "4"
End Select
'update code goes here
Application.ScreenUpdating = True
Unload Me
End Sub