Highlight Cell Based on Value of Another Cell

[PartsPig]

This may require VBA.
I have a formula in a cell that is working as desired to return TRUE when I want another cell in the same row to be highlighted by filling it with purple however I cannot figure out how to get conditional formatting to do this. The formula in said cell is the AND statement below that has 3 conditions to be met. I have the 3 conditions separated below for ease of reading and I have no idea how condition 2 works I just know it does. I'm sure there must be a better way to do this but this is where I am thus far.

The 3 conditions defined:
1 Confirm it is not a formula therefore it has been typed over by something
2 Confirm it it only letters and spaces with nothing else therefore confirming this is the first time this customer's name has been added to the spreadsheet (could have / in it which would be valid but not the first time this customer's name was added)
3 Confirm the value is not equal to void which would satisfy condition 2 but is a valid value that doesn't meet the conditions desired

=AND
(
NOT(ISFORMULA(Table2[@Customer])),
IF(ISNUMBER(SUMPRODUCT(SEARCH(MID(Table2[@Customer],ROW(INDIRECT("1:"&LEN(Table2[@Customer]))),1)," abcdefghijklmnopqrstuvwxyz"))),"true","false"),
Table2[@Customer]<>"void"
)

Like I said, the current form of the formula is working as desired and is not the focus of this question but any and all advice to make the formula easier to follow (especially condition 2) would be appreciated. Ultimately I would like to remove the formula from the spreadsheet altogether and have it either in a conditional format rule or in VBA.

 

[StephenCrump]

The second part of your formula splits out the individual characters in [@Customer] and checks they each match the a-z or space characters (And as Search is not case-sensitive, A-Z will also be OK).

Do you have the new REGEX functions? If so, you could use:

=LET(c,[@Customer],AND(NOT(ISFORMULA(c)),REGEXTEST(c,"^[a-zA-Z ]*$"),c<>"void"))

Or in a conditional formatting formula:

=LET(c,INDIRECT("Table2[@Customer]"),AND(NOT(ISFORMULA(c)),REGEXTEST(c,"^[a-zA-Z ]*$"),c<>"void"))

 

[PartsPig]

The second part of your formula splits out the individual characters in [@Customer] and checks they each match the a-z or space characters (And as Search is not case-sensitive, A-Z will also be OK).

Do you have the new REGEX functions? If so, you could use:

=LET(c,[@Customer],AND(NOT(ISFORMULA(c)),REGEXTEST(c,"^[a-zA-Z ]*$"),c<>"void"))

Or in a conditional formatting formula:

=LET(c,INDIRECT("Table2[@Customer]"),AND(NOT(ISFORMULA(c)),REGEXTEST(c,"^[a-zA-Z ]*$"),c<>"void"))

That worked perfectly and greatly decreases the confusion when looking at the formula. Thanks for the tip!!!

Unfortunately I can't seem to get it to work in conditional formatting...
Ultimately I would want it to change the format of at least 2 different cells in the same row, E and G and maybe H(undecided).

 

[Fluff]

You need to use "Use a formula to determine..." ie the last option on the screen you showed.