Limiting user's table editing options

[Anton_Rybak]

Hello,

I’m trying to make only John Smith can edit/delete the record of this company (Apple Inc.), since he is “App Manager”.

In Companies table I set the following formula:
IF([Company App Manager] = LOOKUP(USEREMAIL(), Users, User EMail, User ID), “ALL_CHANGES”, “READ_ONLY”)

When tested, it show that returned value is ALL_CHANGES, but when saving, it gives an error:
Table ‘Companies’ has an invalid update mode expression ‘=IF([Company App Manager] = LOOKUP(USEREMAIL(), Users, User EMail, User ID), “ALL_CHANGES”, “READ_ONLY”)’. Unable to find column ‘Company App Manager’

What is the problem?
Thank you!