identifying alphabetic sequence, help with nested IFS or new solution?

[AVRAHAMROOS]

Given a column of random letters, I want to identify sequences of a minimum of 3 consecutive letters from the alphabet. For example, if the following letters are given in a column: a,b,c,x, l,m,n, p,g,m,n,o,p,p,g (series1) or a,b,c, k, l,m,n,p,g,m,n,o,p,p,g (series2), I want to get TRUE for the letters in bold.

I have created a complicated nested IF formula for cell 3 which I copy with autofill downwards in the column (I deal with cells 1 and 2 differently):
=IF(C3="","",((IF(CODE(C5)=(CODE(C4)+1),IF(CODE(C4)=CODE(C3)+1,TRUE,(IF(CODE(C2)=CODE(C1)+1,FALSE))),(IF(CODE(C3)=(CODE(C2)+1),IF(CODE(C4)=(CODE(C3)+1),TRUE,IF(CODE(C2)=CODE(C1)+1,TRUE,FALSE)))))))

The formula works (!), except in cases where two series meet or are separated by one unrelated character. In series 1 "x" (cell 4) is marked TRUE (while this should be FALSE) and in series 2 "c" (cell 3) is marked FALSE while this should be TRUE.

My questions:
1. What can I do to solve this?
2. Is there maybe a much easier way to achieve the desired result?

THANK YOU!!

 

[Snakehips]

AVRAHAMROOS,

Still a lengthy formula but maybe this will do it...

Excel Workbook
	A	B
3	a	TRUE
4	b	TRUE
5	c	TRUE
6	k	TRUE
7	l	TRUE
8	m	TRUE
9	n	TRUE
10	p	FALSE
11	g	FALSE
12	m	TRUE
13	n	TRUE
14	o	TRUE
15	p	TRUE
16	p	FALSE
17	g	FALSE
Sheet1

Hope that helps.

 

[AVRAHAMROOS]

AMAZING. Thank you SO much!
I have received a lot of help these weeks from friendly people on this forum. Thanks to them I have managed to build a complicated tool with excel which will help me with my research. This was the last problem I had to solve. My tool is ready now. Thank you all very much!

 

[Snakehips]

You are welcome. It's satisfying to be able to help. Good luck with your project.

 

[AVRAHAMROOS]

Just to show what you have helped built:
https://docs.google.com/document/d/1dwFQvAZcL73OYXD-ykiY_4_hJGqi_nCQ9GN9OlaoKWM/edit#

 

[Snakehips]

Brilliant. For me as an engineer, an unexpected application of Excel. Just shows how useful and adaptable Excel is.