Try this:
Crate a ComboBox and call it ComboBox1 (it's default name)
Crate a doc variable and call it dropdown
Copy and past this into your VBA Code:
Private Sub UserForm_Initialize()
With ComboBox1
.AddItem " "
.AddItem "Blah"
.AddItem "Yada"
.AddItem "Bada"
.AddItem "Bing"
End With
End Sub
Private Sub CommandButton1_Click()
Dim dropdown As MSForms.ComboBox
With ActiveDocument
.Variables("dropdown").Value = ComboBox1.Text
.Fields.Update
End With
Me.Hide
End Sub