I'm programmatically generating some formatted output that generates a cell in the form of a Cell[] expression. For instance, the output might be

cell = Cell[TextData[{"Function ",
    Cell[BoxData[FormBox[RowBox[{"f","(","x",")"}],
        TraditionalForm]], FormatType->"TraditionalForm"]}],
   "Subsection"];

(where $f(x)$ will actually be some complicated expression). How can I get the rendered Cell expression displayed in the notebook temporarily during evaluation?

I can display it (permanently) in the notebook using CellPrint:

I can display text temporarily using PrintTemporary:

But combining them doesn't work, because PrintTemporary assumes its argument is an expression to print rather than a box structure:

Adding DisplayForm doesn't work; it seems DisplayForm only works for boxes when not wrapped in a complete Cell expression:

So I really need a CellPrintTemporary function.