convert view to function

Hi,

I have a view that are used to structure data and I have several reports using this view. One report could for instance use following query commands:
Select case..., sum(...) from view join ... Group by ..., ... Order by...

Now I need to do some more stuff in the view that I think is not possible, so I think I will rewrite this view as a function instead.
Is this a good idea? Is it possible to write for instance:
Select case..., sum(...) from function() join ... Group by ..., ... Order by...
How is performance for function vs view?

Thanks /Magnus

Magnus Burk