Deductions & credits

The amount for each year would be on Form 8829 line 41.  As long as your home office space was the same each year, you can easily take that amount and multiply it by the time you used the home office.  This is because the depreciation is calculated using the Straight Line method with is the same amount each year.  Don't forget to adjust the amounts you didn't get the full year's worth (first and last year using that home).