Gaussian fit with baseline subtraction

I have a curve.. and i want to fit gaussian function on it.. but not on full curve.. only on a part of it.. like if x range of full plot extends from 1 to 10 then i have to do gaussian fiting only on the plot between 4 to 7 .. and since y values are varying from like 10 to 30 and values in that part are from 15 to 23 so for that i have to do baseline subtraction.

Can anybody help me with above program.. I will be very obliged.

Thanks