Is there any way a workflow to be stopped following a change in metadata

Dear All,

Is there any way a workflow to be stopped or to exit in a specific direction if there is a change in the metadata of the document?
Our customer wants to be able to stop already running tasks if he for example puts a stamp changing so that the index entries of the document.

I do this sometimes.  You can put a Condition node inline if you want to check while an item is flowing through a set of workflow actions.  Something like DW_MyField = "StopThisThing" and exit the condition node to the end of the workflow or whatever else you'd want to do with it.  If the item is sitting in a task then you can use the Due Date function to cycle it out of the task and send it to the same kind of Condition node to check to see if the exiting data condition exists and then either flow it out to where you want it to go or back into the task to continue waiting for attention.  I usually have this kind of thing checked daily but you could set the due date for whatever it allows and have the check performed when you want to have it performed.

It's not instant, but it does work.