annual part price reduction formula

See attached.

Ok. Changing to your presentation and getting the same results. See attached.

Don't believe that function exists. However a User Defined Function (UDF) could be created in VBA.

You could copy and paste this as instructed below

Function Discount(Price As Double, Yr1, Yr2, Yr3, Yr4 As Single)
    Discount = Price * (1 - Yr1) * (1 - Yr2) * (1 - Yr3) * (1 - Yr4)
End Function

Open your VBE by Alt +F11
Click on Insert --> Module
Paste this code into the window that opens on the right
Save it.
Close the VBE

Now with your spreadsheet open, click on the fx Function Address
Search for UDF and select Discount.
Complete the form as you would for any other function.

Oh, importantly, if you save this in the workbook, you must save the workbook as an .xlsm file if you are using 2007 or later.

Maybe ...

	A	B	C	D	E	F	G	H
1	Part	Initial	Year1	Year2	Year3	Year4	Final
2	A	$100.00	3.0%	5.0%	2.0%		$ 90.31	G2: =B2*PRODUCT(INDEX(1-C2:F2, 0))
3	B	$100.00	1.5%	2.0%	1.6%	3.0%	$ 92.14