Can I use LEFT function in VLOOKUP?

Hi,

Due to privacy policy, I am only able to upload a tiny part of my spreadsheet but I hope it is enough for one of you clever people to help me. Basically, I need to return the name of the area code in the spreadsheet 'table'. I am trying to only look up the first 4 digits of column j because if I try to convert it in the document before using vlookup it doesn't seem to work because I am lookinp up a formula rather than an actual value in the cell.

Does anyone know if it is possible to use this calculation? (cell A2 on the attached)

=IF(ISERROR(VLOOKUP(LEFT(J2,4),'Area Codes'!A:B,2,FALSE)=TRUE),"n/a",VLOOKUP(LEFT(J2,4),'Area Codes'!A:B,2,FALSE))

Thanks in advance and thank god for this forum.