Working out percentages

Hi,
I need a formula to help work out percentages, if someone would be kind enough to help please.

if C11 = 579 (this is the figure I need to be within 2% of) and I get results in A11 of 581 (High reading) and B11 of 577(Low reading) How do I get the percentage high of the high reading in D11 and the percentage low of the low reading in E11,

Hope this isn't confusing,

Thanks for your time,

Lurch.