How to collapse change list?

The source code is under control of ClearCase. Modified files are not checked in yet. I created a review, added review material using the Client UI, clicked on "Annotating". Later I made more change on one file, then I use "refresh reviews" in the client UI to update the review. Now I found two changes in the review. Nobody accessed the  review yet. Are there any ways for me to collapse the two changes into one? Thanks.