IF function question

[EV]

Hi, I need to create a formula that looks at several cells, and
performs several functions and every time I try I get an invalid or
other error, so I'm having trouble with the syntax. I appreciate any
help with this problem. Thanks so much!

I need the formula to say:

If fee (N7) equal "YES" then,
In 'Total Fees' cell (O7)
If price (G7) equals $0 - $25, then multiply by 5.25% (other
worksheet!I27)
or
If price (G7) equals $25 - $1,000 then multiply by 5.25% (other
worksheet!I27) of the initial $25 ($1.31), plus 2.75% (other
worksheet!I28) of the remainder (up to 1000)
or
If price (G7) equals over $1,000 then multiply by 5.25% (other
worksheet!I27)of the initial $25 ($1.31), plus 2.75% (other
worksheet!I28) of the initial $25 - $1000 ($26.81), plus 1.50% (other
worksheet!I29) of the remainder ($1000.01 and up)
else,
If fee (N7) equal "No" then, "0"

Thanks for any help !!!
Regards,
E