You could create you own custom action. The docs have some information about how to do this.
http://www.worldviz.com/vizhelp/VizH...wn_actions.htm
Your custom action could take as an argument the new center point of the object. In the action code first you will need to get the position of the object using the viz.ABS_GLOBAL flag. Then you will set the center of the object using the value passed in. Then you reset the position to where it originally was, again using the viz.ABS_GLOBAL flag.