How to clear formula without clearing cell contents

Hi,
If I set some formula using some cells' values. And after using this formula
I want to remove the formula and leave the content of those cells as it is.

e.g.
Id I set the (D1+E1) and set this to 15 cells in that column A1 to A15. Now
I want to delete the column D and E but don't want to disturb the contents
of column A. For this I require to delete the formula without clearing the contents of the column(I think).

Please let m eknow how can I do this?

Thanks, that is also one way.

But is it possible to remove just formula of group of cells without removing
values?