Yes and no. As Mark says above it depends on your speedlight. If you have a TTL speedlight then its pretty easy. If you go manual and have a flash that is capable of changing its power output then again yes but its a bit more work on your part.

In the latter what you want to do is meter for ambient then set your flash for a stop higher than ambient if you're doing portraits or between a 1/3rd to a 2/3rds lower if its still life. Its really a case of how much influence and what kind of look you're going for with the flash. If you have a Dslr you can use that to meter the flash output and then use it as a reference for the film, or use a flash meter (which are worth their weight in gold) or run a test roll through the camera with various settings of power for the flash at all the angles.