force alignment?

I know how to format a cell so the alignment is centered both vertically and
horizontally.

However, if a user copies/pastes text from, say, Microsoft Word into a cell
in Excel, it positiions it to the left at the bottom of the cell. Not a big
deal, really, but I would like for all of the cells to be centered
horizontally and vertically.

Is there a way to force a cell to align its contents centered, even if it is
copied and pasted from another document, rather than manually entered with a
cursor inside the cell? (Perhaps a macro could check a cell once the enter
key is pressed or the focus leaves a cell in some way?)

Thanks!