ZSE Controller described airspace incursion event when they; distracted with military aircraft operations; failed to make a timely hand off; noting enhanced automated procedures may have prevented the incident.

Narrative

I was working sectors 7 and 11 combined; which is normal at that time of day due to lower traffic volumes. Air Carrier X was northbound toward Edmonton Center on J537. Due to lack of automation between ZSE and Edmonton; coordination was accomplished per LOA's regarding Air Carrier X's estimated boundary crossing time at ONEAL. As Air Carrier X continued northbound through my airspace I accepted hand-offs on two Military aircraft who were requesting to join up for aerial refueling. The intended join up point is approximately 100-150 miles southwest of ONEAL. As is often the case; the timing of the join was not perfect; and as a result the two aircraft had several requests to accommodate. I became focused on the two military aircraft and their join up; and lost track of Air Carrier X's position. Having gotten the military aircraft joined and cleared down track; I returned to my scan and noticed Air Carrier X approximately 5 miles north of the border; at nearly the same time; Edmonton center called to inquire about the hand off. There was no loss of separation and the Edmonton controller was not especially bothered or upset with the situation. Due to the prior coordination; he had been expecting Air Carrier X and; as is normal; it seemed as though he had had RADAR on him well prior to the boundary. Overall the situation was harmless; and the aircraft involved were not aware of any incident. Regardless; it was a stark reminder to not get too focused on one particular area or aircraft; especially during lower traffic volumes. Recommendation; continued development of automation between US and Canadian centers would be beneficial; especially the development of an automated hand off. Such automation would have probably prevented this incident; however; it was really my alternate focus that was the leading factor.