Formula to calculate Inflation adjusted returns for an index

[polly95]

Hello, I am a newbie here so hopefully this is suitable for this forum.

I am currently trying to find the inflation adjusted returns for a particular energy index just over a 5 year period.
I collected the CPI data for the FRED and collected and calculated the returns for the index from Bloomberg data.

I am unsure what formulas I should be using to 1. find the correct CPI and 2. how to adjust the returns for the index with inflation. Below is the following of how I have attempted some steps.
I could very well be completely off on my formulas but this is all I could find on the internet.

Any help would be amazing.

CPI .xlsx
	A	B	C	D	E	F
1
2	Date	CPI (FRED)	CPI/100			Monthly returns Index
3	01/03/21	264.793	2.65	0.6%		-6.97
4	01/02/21	263.161	2.63	0.4%		-13.39
5	01/01/21	262.231	2.62	0.3%		6.28
6	01/12/20	261.560	2.62	0.2%		19.33
7	01/11/20	260.927	2.61	0.2%		20.54
8	01/10/20	260.462	2.60	0.1%		5.76
9	01/09/20	260.149	2.60	0.2%		7.60
10	01/08/20	259.511	2.60	0.4%		18.68
11	01/07/20	258.604	2.59	0.5%		15.74
12	01/06/20	257.282	2.57	0.5%		5.18
13	01/05/20	255.942	2.56	-0.1%		10.23
14	01/04/20	256.192	2.56	-0.7%		11.76
15	01/03/20	257.989	2.58	-0.3%		-23.02
16	01/02/20	258.824	2.59	0.1%		2.23
17	01/01/20	258.687	2.59	0.2%		3.43
18	01/12/19	258.203	2.58	0.1%		7.06
19	01/11/19	257.989	2.58	0.2%		2.79
20	01/10/19	257.387	2.57	0.3%		-1.95
21	01/09/19	256.532	2.57	0.2%		-0.77
22	01/08/19	256.118	2.56	0.1%		1.57
23	01/07/19	255.925	2.56	0.2%		0.59
24	01/06/19	255.423	2.55	0.0%		6.65
25	01/05/19	255.371	2.55	0.0%		-2.01
26	01/04/19	255.326	2.55	0.5%		3.68
27	01/03/19	254.147	2.54	0.5%		-0.30
28	01/02/19	252.969	2.53	0.2%		2.58
29	01/01/19	252.441	2.52	0.0%		14.32
30	01/12/18	252.493	2.52	-0.1%		-6.94
31	01/11/18	252.822	2.53	0.0%		10.09
32	01/10/18	252.899	2.53	0.3%		-5.62
33	01/09/18	252.183	2.52	0.2%		-2.02
34	01/08/18	251.735	2.52	0.2%		-4.85
35	01/07/18	251.345	2.51	0.1%		4.03
36	01/06/18	251.152	2.51	0.1%		-9.31
37	01/05/18	250.786	2.51	0.2%		-2.36
38	01/04/18	250.275	2.50	0.3%		4.03
39	01/03/18	249.517	2.50	0.1%		0.50
40	01/02/18	249.300	2.49	0.2%		-2.40
41	01/01/18	248.721	2.49	0.4%		2.77
42	01/12/17	247.736	2.48	0.1%		5.29
43	01/11/17	247.378	2.47	0.3%		-4.37
44	01/10/17	246.657	2.47	0.0%		4.08
45	01/09/17	246.551	2.47	0.5%		-1.90
46	01/08/17	245.205	2.45	0.4%		0.41
47	01/07/17	244.280	2.44	0.0%		5.40
48	01/06/17	244.218	2.44	0.1%		-0.20
49	01/05/17	244.069	2.44	-0.1%		1.47
50	01/04/17	244.274	2.44	0.2%		-0.80
51	01/03/17	243.766	2.44	0.0%		-1.48
52	01/02/17	243.872	2.44	0.1%		4.46
53	01/01/17	243.620	2.44	0.4%		4.26
54	01/12/16	242.637	2.43	0.3%		0.13
55	01/11/16	242.026	2.42	0.1%		-9.28
56	01/10/16	241.741	2.42	0.2%		-2.93
57	01/09/16	241.176	2.41	0.3%		-1.72
58	01/08/16	240.545	2.41	0.2%		1.08
59	01/07/16	240.101	2.40	-0.1%		3.59
60	01/06/16	240.222	2.40	0.3%		1.74
61	01/05/16	239.557	2.40	0.2%		-6.01
62	01/04/16	238.992	2.39	0.4%		-0.86
63	01/03/16	238.080	2.38	0.3%		9.40
64	01/02/16	237.336	2.37	-0.1%		-2.37
65	01/01/16	237.652	2.38	0.0%		-11.99
66	01/12/15	237.761	2.37761
CPI

Cell Formulas
Range	Formula
D3:D65	D3	=(C3-C4)/C4
C3:C66	C3	=B3/100