I'd do 2 things (at least!). Is there one person who you can count on to relieve you if you need to run to the bathroom for a few minutes? I would feel better just knowing that I had an escape plan. They don't have to know your whole ibs story, non-ibsers also go to the bathroom and sometimes worry about whether they will be able to get there when they need to - so its not an outrageous request. THe other thing I would do, is the same as my little daughter does - bring some comfort objects with you - for her its her pacifier and blanky but I would have your own tea mug and tea bags and maybe a microwave heatpack at work as well as any rx that you should have on hand. A sort of safety kit. I try to be prepared for things like that so I can hopefully worry about the possibilities less. We've all been there!
-------------------- Ladies & gentlemen take my advice, pull down your pants and slide on the ice.