You can't. That is not allowed by Excel.

A function used in a cell can only return a value to the cell - it can't
change the "environment".

http://support.microsoft.com/default...b;en-us;170787
XL: Custom Functions Can't Change Microsoft Excel Environment

Regards,
Tom Ogilvy

"Pierre Laporte" wrote in message
.. .
When I use the following code from a macro call on the menu of Excel it
works fine (changes the format of the top leftmost cells of the sheet but
when I execute it from a function that is used in a cell of the sheet it
does not work.
How can I change the format or content of cells in a spreadsheet from
within
a vusual basic function called in a cell ?
_______________________________________________

Sub upc()

Dim myCell As Range
Set myCell = Worksheets("Feuil1").Range("A1:C1")
With myCell.Font
.Bold = True
.Italic = True
End With

End Sub