Highlight highest and lowest value

What do you mean by highest/lowest in row compared to A?
Do you mean higher/lower in row compared to value from A?
Highest/lowest in row is highest/lowest in row.

let's say that column A has the highest or lowest price in the row as compared to columns B C and D, how do you want that shown?
And if column A is in the middle, how do you want the highest shown and the lowest shown, different background fill colors for each?

There is an easy formatting rule that you can use for this, go to conditional formatting >> new rule >> format all cells based on their values >> 2-color scale; pick a color for the lowest value and a color for the highest value (I used white fill for lowest and green for highest) then hit ok, then use format painter to extend it for all your rows.
You'll have a mixture of colors but you'll see your highest and lowest for each.

another way... CF >> use formula to determine which cells to format >> =A2=Min($A2:$D2) >> pick format >> Ok then apply.
Add another rule (follow above) =A2=MAX($A2:$D2) then pick format, ok and apply.
finally use the format painter across the whole range and the rows.
now you have a two color set instead of the ranges I gave you in post #4.