Rear Wheel Bearing noise

[Grant Dion]

Anybody
Is it possible to somehow inject some liquid grease into the rear wheel
bearings? My right rear is making a howling sound, like large off road type
tires would on a truck. The noise gradually grew louder. I will ultimately
replace both rear bearings, but would like a stop gap, and I need to log
400-500 miles this weekend on the car. 

I believe the bearings have a plastic cover, and hope that somebody has had
short term success by injecting spray grease. PLEASE REPLY ASAP! 

Thanks

Grant in Colorado Springs