Sure.
In admincp under vbcredits menu, click Activity Amounts Configuration.
If you dont have an Activity action, select it from the dropdown at the bottom and click Go. Fill it out as you see fit.
Then in the vbcredits menu again, click Action Specific Configuration, and set activity interval to 1, reference date can be left as any day, and activity requirement to Sign on.
That will trigger the activity action each day the user logs on.