I have a similar situation with my driveway and have had decent
success with products available at Home Depot and Lowes.
Unfortunately, cant tell you the names off the top of my head...but
both stores have the same stuff, just different brand names.
Basically, its a black, paste-like mixture that comes in a small
bucket. You lay it on with a trowel and work it into cracks and/or
reform missing portions with the trowel. It will dry in the sun and
harden in place. Then once its fully set, you apply the regular
sealant to finish the job. I'm sure Steve is right that this is only a
temporary fix, but we also arent to a point where we can afford a
complete redo of the driveway, and for us this has worked decently. A
couple things to note from my experience working with this patch
material.... Make sure you use it on a sunny day (tried on a colder
day, and the material never fully "cured"...cracked soon
after)...also, make sure you clean out as much grass and junk from
below the crack and really pack it in to avoid any gaps underneath -
so that it doesnt settle and crack. The manufacturer says this stuff
should not be used for holes larger than 6" I believe, but I've never
had a need to do that, so cant tell you if it would work well for
large holes. Hope that helps.