A method for selecting an optimal trajectory of a wellbore while drilling the wellbore and a computer program having instructions for the same are disclosed. The method and program may include obtaining data, such as real-time date, related to the wellbore and obtaining data related to drilling limitations. The method and program also obtains data related to production considerations or drilling considerations. A target is selected and the optimal trajectory is selected from possible trajectories to the target. Ideally, the optimal trajectory conforms with the drilling limitations and satisfies one or more of the production considerations or drilling considerations.