How to display a omni-comletion menu from a vim script function?

[Thomas]

Hi,

I would like to use the new vim7 drop-down menu that is used with the 
new omni-completion from a vim script in order to let the user select an 
item from a list.

I figured I could temporarily set &omnifunc and use this to build the 
list. But I wasn't able to find a way to trigger the display of the menu 
from within a vim script.

Does somebody have an idea of how to display the menu?

Say, we have:

fun! MyComplete(findstart, base)
...
endf

fun! DoSomething()
    let omnifunc = &omnifunc
    let &omnifunc = 'MyComplete'
    try
        +++DISPLAY MENU+++
        return 0
    finally
        let &omnifunc = omnifunc
    endtry
endf

How would the "DISPLAY MENU" part look like?

Regards,
Thomas.