Warning!! Complicated question. Advice needed.

[Michael Linquist]

Hello all, this is a very complicated question so I will try to spell it out as clearly as possible with an example. 

Mary wants to sell her house. The ARV of her house is $300,000. I offer to Straight option Mary's house with 10 day auction/general sale strategy (basically I will take the highest bid).

Mary agrees to my deal. I get Mary's house under straight option contract for $200,000. 

However, can I add a contingency clause/contract to the straight option that increases the amount Mary will receive based on the highest bid I receive when I close?

So, if I sell the house for 260,000. Instead of taking 60,000 from Mary, the contingency contract would allow the Straight option price I made with Mary to increase, so that she is not screwed out of 60,000 of equity and I feel like a crook.