So, as you expected it does not work. The error is:
No signature of method: java.lang.String.getStates() is applicable for argument types: (com.agile.api.StatusConstants) values: [3:TYPE_RELEASED]
Possible solutions: getBytes(), getBytes(java.lang.String), getBytes(java.nio.charset.Charset), getClass(), getChars()

The Event trigger is Change Status and it is triggered by the Acknowledge button.

Matt, 

Thanks for all helping. I was thinking it would be easier. I am not a programmer, I just know a little about codes. I can´t do that and because of that I will give up this and I will look for a different way to move this status.

Again, thanks a lot for you time.

Hi Matt,

My code was pretty much equals yours. My mistake was that I am passing the value accepted instead of approved and because of that it was in a infinite loop.
Now it is working but my code does not have the try {. Could you please explain me why the try {?

Hello,

Could you please provide a example code with the initial steps as well? How to load the change and set the Workflow?

Thanks!

Arif, thanks a lot for answer this!

I think my problem is different. I need a groovy which will change the Workflow to cancel or released depeding on the value of a change attribute.
For example: If the value of attribute x = accepted than, after the event trigger, workflow status should change to released. If the value of attribute x = denied than the workflow status should change to Canceled. 
I could make it almost work using setAttributebyValue but it not work since the workflow status cannot be change in this way since there is no permission to change. I think I need to use something like changeStatus(Released), but I do not know how.

Could you please help me?

Thanks in advance!