Care plans & sig changes

How long do you have to update care plans after a resident has had a sig change? I did a sig change on a resident the 1st part of Nov, well she continued to decline, so I updated the care plan for the later part of Nov, but I made a mistake and put the 25th on it, instead of the 24th, I'm human right ? Any way, this resident got a NG tube on 11/23/08 but I left the eating = ext x 1 assist, my theroy was the NG was a acute thing, not for the care plan at that time, I always thought that you have 14 days to do or update your care plans from the date of the sig change. Any one have anything they can add? I can't change the care plan because our computer system locks them out if the reisdent leaves the facility and she did, to me it's simply a data mistake, I simply need to fix it, right, or am I like not taking this seriously enough?? Help....