Can I use my RPP contribution from box 20 on my T4 slip to reduce the amount I owe for my home buyers repayment plan?

[TurboTaxKim]

No, your Home Buyers Plan repayment must come from a contribution to a Registered Retirement Savings Plan (RRSP). The amount in Box 20 is a Registered Pension Plan set up by your employer (also called a "company pension"). 

Here's some more information from Turbotax you might find helpful: Repaying Withdrawals Under the Home Buyers’ Plan