You can bid a line at the lower end of the credit range for the month, then drop what ever trip(s) to get you down to a part time, or zero time line.

One caution for new hire pilots employing this strategy (since recently hired new hires will be line holders very quickly). In order for you to complete your probationary period at UAL, you must have 12 months on property and at least 165 days of service to the company. Most pilots have no trouble meeting this in the first 12 months on property; however, if you only spend a couple of months on reserve and then start dropping trips each month, one might find themselves on probation for longer than the normal 12 months until the 165 day requirement is met. Not a huge deal to some, but it would be to me.