The ubutton, and indeed just about every UI object in Max, has an 'ignoreclick' attribute that can be set or cleared.

This type of question is asked so frequently that it's probably worth my submitting the following pseudo-contribution to the "Did you know?" series.

Did you know that Max will help you set up messages to control attributes of objects? Select the object you want to control, and type Command-I (Control-I in Windows) to open the object's Inspector window. Most of the object's alterable traits shown in that Inspector window can also be controlled by a message in a Max patch. In the Inspector window, click on the name of the trait you want to control, drag that name into your Patcher window, and release it. You'll be presented by a contextual pop-up menu offering to set up an object that will permit you to control that attribute in your patch. This trick is also a good way to learn the names of attributes that you might otherwise not know. Happy patching!

Hi Christopher That's exactly what I needed. I was aware of the attributes but I didn't know about the drag to patcher thing. Sorry about late reply. Thanks Liam.