you can do it manually, or
after your federal is completed and filed,
start amending your state return
and delete the 1099-R that showed the distribution in the first place.
That should have the desired result on your state tax return.
Iowa says:
"An amended Iowa return can be filed electronically."
you can't do that if you do a manual override.
Note: be careful. you only get one amendment e-File.
