Conditional Formatting using different expiry dates

Hi all,
i'm new to this forum and have tried to research this answer but cannot find a solution so here goes!
I am using a spreadsheet to track training courses for personnel to check when their training expires. I require a cell to change to Amber 30 days prior to expiry and red once expired. I have found answers regarding conditional formatting referring to todays date, but i require the formula to start from any date i input ie. one persons training took place 1/4/12 and runs out in 12 months, the 2nd person took the training on 10/5/12 and that also runs out in 12 months. Both cells need to change to amber 30 days prior to expiry but they start on different days!!

Please help!!!!

Many thanks from an excel beginner!!!