You could do that by inserting a line-break at the appropriate point in the text. The line-break insertion could be semi-automated with a macro. For example:
Sub Demo()
Dim i As Long, sWdth As Single
With Selection
If .Information(wdWithInTable) = False Then Exit Sub
With .Cells(1)
sWdth = .Width - .LeftPadding - .RightPadding
With .Range
.Font.Scaling = 100
If .Characters.First.Information(wdVerticalPositionRelativeToPage) <> _
.Characters.Last.Previous.Information(wdVerticalPositionRelativeToPage) Then
.FitTextWidth = sWdth * 2
End If
For i = 1 To .Characters.Count
If .Characters(i).Information(wdHorizontalPositionRelativeToTextBoundary) > sWdth Then
.Characters(i).InsertBefore Chr(11): Exit For
End If
Next
End With
.FitText = True
End With
End With
End Sub
With the above macro, anything more than one line's worth of content will be rescaled to fill two lines.