Nice one Jude. You know I have been using this program for 10 years, and every time I think I know it someone shows me there is another trick hidden somewhere inside.
Not only can you set an absolute duration that way but you can add or subtract a global amount of time to clips of different durations.
Select all the clips you want to change in the browser, right click in the anamorphic column and click "yes". Not just that, the right clicking thing also works if you want to tag multiple items in the logging columns, eg. If you want to set a bunch of clips as "broll", for example.