Sorry, I missed this the other day

What you propose is easy enough with content controls. You need a list box to make the selection, a rich text control for the related value and a macro to evaluate the selection(s) and fill the text control(s) appropriately.
You may find
Insert Content Control Add-In useful.
The macro must go in the ThisDocument module of the form template and would be something like:
Code:
Private Sub Document_ContentControlOnExit(ByVal ContentControl As ContentControl, Cancel As Boolean)
Dim oCC As ContentControl
With ContentControl
If .ShowingPlaceholderText = False Then
Select Case .Title
Case Is = "System"
Set oCC = ActiveDocument.SelectContentControlsByTitle("Queues Impacted").Item(1)
Select Case .Range.Text
Case Is = "AS400"
oCC.Range.Text = "NA"
Case Is = "Genesys"
oCC.Range.Text = ""
End Select
Case Else
End Select
End If
End With
Set oCC = Nothing
End Sub
The first level of case statements are your list boxes. The second the results according to the selected values.