Macro needed to create formula by cell not value

I am working on a budget workbook and in column I (I5-I1135) I have numbers that I need to upon prompt (such as CTRL C) have the numbers divide by 10 then multiply by 12..

Example:

cell I5 has $3,266,808 (looped from other pages) and I want to upon being on this cell be able to press Ctrl C and have this number divide by 10 then multiply by 12

If possible I would like for it to go back to its original number upon prompt as well

I am using this to compare a prior 10 month year to the new 12 month budget to assure that I am looking at an apples to apples comparison

Thank you in advance for any help you can offer