Nathan Phillips (CW) 2/20/2011 11:06:58 PM
Graham - you could use the button to trigger two different workflow rules. If you filter the two workflow rules differently, one for each of the criteria you want to check for, then only the correct action will trigger. You can set up the trigger in both rules on a checkbox column - the same checkbox column in both trigger. Default it to unchecked. Then trigger a different workflow action in each of the rules.
The only assignment in the button, then, is setting that trigger flag to true. Then clicking the button will always perform the correct action.
If you need to be able to trigger the action again on the same record, then in both workflow actions you can clear the trigger column so that it can be triggered again.