Compare First Name and Last Name in One Workbook with First and Last Name in Another

What I'd like to do is write a function to compare someone's first and last name from one workbook to a table of first and last names in another, uneditable spreadsheet. The function should then mark "Y" if the person has the same full name (i.e. =(First&" "&Last)) or "N" if their full name is not in the other workbook.

What I tried so far was the following:
=IF(AND([Last]='Other Workbook.xlsm'!Table_ExternalData_1[LastName],[First]=INDEX('Other Workbook.xlsm'!Table_ExternalData_1[FirstName], MATCH([Last],'Other Workbook.xlsm'!Table_ExternalData_1[LastName],0))),"Y","N")

Basically my intended logic behind this was as follows:
Search for a last name in the other workbook. If that last name exists, then compare the first names. If the first and last names are the same, write "Y". If not, write "N".

I also tried this much simpler function, which should accomplish the same goal:
=IF(CONCATENATE([First]&" "&[Last])=CONCATENATE('[Other Workbook.xlsm]Sheet2'!$E:$E&" "&'[Other Workbook.xlsm]Sheet2'!$F:$F),"Y","N")

Both functions are not meeting my intentions. If anybody has any suggestions on how to improve my formulas or on why it is not working, I'd really appreciate it the help.

Thanks!

Thank you for your help! Do you know of any way to do it without making a "From non-writable notebook" column? The non-writable notebook contains massive amounts of data.