What is formula =TT(field) and how does it work?

[merreh]

I found a formula =TT(field code) in my spreadsheet, that is somehow converting number values into a letter showing level of service. But I can not find anywhere in the spreadheet, where does it take the value ranges from (like vale 1-4 =A, 5-6= B etc) and I can not find any information on such a formula.

Can anyone help me please?

[#2]

Hello @merreh ,

this is not a built-in Excel function. It could be a user-defined function created with VBA or it could be from a 3rd party add-in.