Basic Question. How to ref a cell in vlookup (Vlookup Value) and get results.

E.g. I've Formula to get my Sheet name in A1,

Using this formula to get sheet name >> =MID(CELL("filename",A1),FIND("]",CELL("filename",A1))+1,255)

Now I want Vlookup to lookup A1 & then carry on with the process but my formula fails as A1 is not a binary Value I guess?

how to treat A1 as a Number or Text?