Alpha Numeric Validation in Microsoft Excel - excel

Question

1- I'd like to use a validation rule for an input cell where the entry must be 7 or 8 alphanumeric characters long
2- at the start of the string Alphas used must be 1 or 2 characters and uppercase.
3- at the end of the string Numerics will always be 6 characters long.
4- The following type of entries are required to be validated
FD456789
X256325
Z899666
DQ985421
FD000052
5-I have created a validation formula. it works fine except it cannot validate 2nd character as alphabate in the string. i used AP656569 and A5656569 for testing. it should allow only AP656569, but on the contrary it is allowing both strings.
Formula: =AND(OR(LEN(A3)=7,LEN(A3)=8),ISNUMBER(VALUE(RIGHT(A3,6))),IF(LEN(A3)=7,NOT(ISNUMBER(VALUE(LEFT(A3,1)))),ISTEXT(MID(A3,2,1))))

Answer 1

You may try:
=AND(AND(LEN(A1)>6,LEN(A1)<9,ISNUMBER(RIGHT(A1,6)*1),CODE(A1)>64,CODE(A1)<91),IF(LEN(A1)=8,AND(CODE(MID(A1,2,1))>64,CODE(MID(A1,2,1))<91),1))
=AND( - Let's check two things:
AND( - Check if multiple conditions are TRUE:
LEN(A1)>6 - Check if string is over 6 char.
LEN(A1)<9 - Check if string in under 9 chars.
ISNUMBER(RIGHT(A1,6)*1 - Check if 6 rightmost characters make up a numeric value.
CODE(A1)>64,CODE(A1)<91 - Check if leftmost characters is in class [A-Z].
IF( - Check the following:
LEN(A1)=8 - Check if the lengths is actually 8.
AND( - If TRUE then check the following:
CODE(MID(A1,2,1))>64,CODE(MID(A1,2,1))<91 - Check if 2nd char is in class [A-Z].
1 - If the length is not false, it will still be 7, therefor we return a 1 (equal to TRUE), to not mess with our parent AND().
You can apply this to your custom validation rule as a formula if you want to avoid false data, or as mentioned in the comments to conditional formatting if you want to be able to show false data after it being entered.
Alternatively, if you have Excel 2019 or higher, and you like code-golf you could use:
=AND(ISNUMBER(RIGHT(A1,6)*1),CODE(A1)>64,CODE(A1)<91,SWITCH(LEN(A1),7,1,8,AND(CODE(MID(A1,2,1))>64,CODE(MID(A1,2,1))<91),0))

Answer 2

Your conditions do not exclude a string like A1234567 (1 capital letter, 7 digits). According to your conditions and assuming your string is in cell A1, this formula should work:
=AND(OR(LEN(A1)=7,LEN(A1)=8),OR(IFERROR(LEFT(A1,1)*1,0)=0,AND(IFERROR(LEFT(A1,1)*1,0)=0,IFERROR(LEFT(A1,2)*1,0)=0)),UNICODE(A1)=UNICODE(UPPER(A1)),UNICODE(MID(A1,2,1))=UNICODE(UPPER(MID(A1,2,1))),IFERROR(MID(RIGHT(A1,6),1,1)*1,0),IFERROR(MID(RIGHT(A1,6),2,1)*1,0),IFERROR(MID(RIGHT(A1,6),3,1)*1,0),IFERROR(MID(RIGHT(A1,6),4,1)*1,0),IFERROR(MID(RIGHT(A1,6),5,1)*1,0),IFERROR(MID(RIGHT(A1,6),6,1)*1,0))
It's basically an AND function that contains:
a condition to check for the lenght of the string: OR(LEN(A1)=7,LEN(A1)=8)
a condition to check if first 2 characters of the string are letters (only the first or both): OR(IFERROR(LEFT(A1,1)*1,0)=0,AND(IFERROR(LEFT(A1,1)*1,0)=0,IFERROR(LEFT(A1,2)*1,0)=0))
a condition to check if the first character is capital: UNICODE(A1)=UNICODE(UPPER(A1))
a condition to check if the second character is capital: UNICODE(MID(A1,2,1))=UNICODE(UPPER(MID(A1,2,1)))
a condition for each last 6 characters to check if they are numeric (example refers to the first one): IFERROR(MID(RIGHT(A1,6),1,1)*1,0)
EDIT: Improvements
The formula can be improved like this:
=AND(OR(LEN(A1)=7,LEN(A1)=8),OR(IFERROR(LEFT(A1,1)*1,0)=0,AND(IFERROR(LEFT(A1,1)*1,0)=0,IFERROR(LEFT(A1,2)*1,0)=0)),EXACT(LEFT(A1,2),UPPER(LEFT(A1,2))),ISNUMBER(RIGHT(A1,6)*1))
It's still an AND function. This the changes:
it contains a single condition to check if the first 2 characters are capital (previously there were 1 for each character that used the UNICODE function): EXACT(LEFT(A1,2),UPPER(LEFT(A1,2))) [CREDIT: JvdV]
it contains a single condition for the last 6 characters to check if they are numeric (previously there were 1 for each character that used the IFERROR function): ISNUMBER(RIGHT(A1,6)*1)
EDIT: correction
In order to exclude special character, i've edited the formula:
=AND(OR(LEN(A1)=7,LEN(A1)=8),OR(AND(UNICODE(A1)>64,UNICODE(A1)<91,ISNUMBER(MID(A1,2,1)*1)),AND(UNICODE(A1)>64,UNICODE(A1)<91,UNICODE(MID(A1,2,1))>64,UNICODE(MID(A1,2,1))<91)),EXACT(LEFT(A1,2),UPPER(LEFT(A1,2))),ISNUMBER(RIGHT(A1,6)*1))