Hi Brock,
The 'Exit For' was there because your post implied that you only wanted the very next Content Control, not all of them, and you didn't indicate anything about whether the next Content Control had the same tag.
Since it seems only some of the Content Controls have the 'ContainerContents' tag, it would be more efficient to do it this way:
Code:
Dim strTmp As String, i As Integer
With ActiveDocument.SelectContentControlsByTag("ContainerContents")
For i = 1 To .Count
strTmp = strTmp & .Item(i).Range.Text
Next
End With