You may need to give the Colazal a bit more time to have an effect and if asacol was not working for you then what other options have you considered? There are many options out there (..such as lialda, remicade....) so maybe you should discuss them with your GI specialist.
Also, I agree with Heather/Quincy's point about treating UC from both ends (thanks for the prudent advice Heather). After consulting with my doc I have started taking cortifoam to supplement the Colazal treatment and try to get the UC into remission asap.
Have you considered wearing a 'depends' at work till you are able to get the d under control? At least that way you can still continue working.
Also, do you think you might benefit from a second opinion from another GI specialist regarding your treatment, especially the low dosage of colazal compared to the high dosage of asacol that you were on previously?