No problem Eddie. In an event right click and select "New Compound Clip", or hit alt-G.
Step into the compound clip you had previously created in a project by double clicking on it and copy all the content with "cmd-c" as normal, now either double click on the new empty compound clip in the event or right click and select "Open In Timeline", then use the "cmd-v" keyboard shortcut to paste into it.
If you drag this new and, now populated, compound clip from the event onto the compound clip in the main project timeline, wait for it to turn white, let go of the cursor and select "Replace" from the menu that shows up you'll get your replace edit. It won't make any difference to how the project plays back, just that the compound clip in the timeline will now be referencing the event version.