Yes, you need to add the NGUI get Onclick script which is on this forum to the button.
Then add an OnClick action to the Playmaker FSM and then add a set property to a new state in the fsm.
Click the button to hold the playmaker screen whilst you select the script you want to change and drag it to the set property action, you can you select the property you want to control.
Sorry if it's a bit hard to understand. I don't have playmaker in front of me to check the names of everything.