Glenn said:

I lose the battle of grass and other crap in my garden every year. I only
plant corn (3 plantings), a few tomatoes from plants, maybe a couple hills
of cantaloupe and broadcast some flowers across one end.

Is there a pre-emergent that I can use just after the things I want are
above the ground, for the grass that won't kill everything else?

If it's a "pre-emergent", it won't kill anything that's already germinated.
Depending on your location (you were more than a bit vague about that), it
/may/ be too late to apply. Then again, it may not.

--

Eggs

When the only tool you own is a hammer, every problem begins to look like a
nail.