You may create one automation scheme per activity result.
To create a new scheme, go to the Act! Tools menu and look for the Better Last Activity Date Tracking menu item. Click it and click the Add... button of main window.
The following window will pop up:
You first need to select the activity result you want to associate the automation to.
Then you select the date fields you want to update when clearing an activity with the above selected result. You may select one contact field, one company field, one group field and one opportunity field. The contact field will always be used because an activity is always associated with a contact. The company, group and opportunity field will only be used if a corresponding record is associated with the opportunity.
The last 2 options should be self-explanatory.