You could try this. Unfortunately there is no change event for content controls and the code won't fire until the user selects and exits the content control. A userform would probably be better for your requirement.
Private Sub Document_ContentControlOnExit(ByVal ContentControl As ContentControl, Cancel As Boolean)
Select Case ContentControl.Title
Case "A", "B", "C" 'These are the titles of the organization text boxes
BuildOrgList
Case "1", "2", "3" 'These are the titles of the 80 group
'Build80List
End Select
lbl_Exit:
Exit Sub
End Sub
Sub BuildOrgList()
Dim oCCOrgs As ContentControls
Dim oCC As ContentControl
Dim arrChecked() As String
Dim lngIndex As Long, lngChecked As Long
Dim strOrgs As String
lngChecked = 0
Set oCCOrgs = ActiveDocument.SelectContentControlsByTag("Org")
Set oCC = ActiveDocument.SelectContentControlsByTitle("Organizations").Item(1)
For lngIndex = 1 To oCCOrgs.Count
If oCCOrgs(lngIndex).Checked Then
ReDim Preserve arrChecked(lngChecked)
arrChecked(lngChecked) = oCCOrgs(lngIndex).Title
lngChecked = lngChecked + 1
End If
Next
On Error GoTo Err_EmptyArray
Select Case UBound(arrChecked)
Case 0
oCC.Range.Text = arrChecked(0)
Case 1
oCC.Range.Text = arrChecked(0) & " and " & arrChecked(1)
Case Is > 1
For lngIndex = 0 To UBound(arrChecked) - 1
If lngIndex = 0 Then
strOrgs = arrChecked(0)
Else
strOrgs = strOrgs & ", " & arrChecked(lngIndex)
End If
Next lngIndex
strOrgs = strOrgs & " and " & arrChecked(UBound(arrChecked))
oCC.Range.Text = strOrgs
End Select
lbl_Exit:
Exit Sub
Err_EmptyArray:
oCC.Range.Text = " "
Resume lbl_Exit
End Sub