Created Unassigned: Cell format to "Date" [9343]

I'm setting the date using the dd/mmm/yy format as below.

ws.Cells[2,4].Style.Numberformat.Format = "dd/mmm/yy";

It works great. But there is only one requirement.
When the end-user opens the workbook and navigates to the cell in question (say: E2), the formatting drop-down in the Number area of the ribbon must say "Date", not "General" or "Custom".

How do I do that?