how to do "wait_for confirmation" (or similar)

(First of all, sorry if this has been asked a dozen times already, i did try searching the posts)

I have a page for downloading some resources - when the user clicks on the download link there's a wait for anywhere between a few seconds and over a minute while the files are zipped up and prepared for download.  When the file's ready, we shove up a file download dialog, and it's the appearance of this dialog that i'm trying to test.

I can't work out how to do it though - what i want is simple:  like a normal

wait_for(locator)

call, but waiting for the 'your file is ready' dialog instead.   page.confirmation? and page.alert? don't work, i guess because a download dialog is not the same as a confirmation dialog?  anyway - can anyone help?

thanks
max