Multiple Lookup within same cell

[fbenzoni]

Hi,
i'm trying to validate each comma separated value of a string to return the errors(values not found)
in the file attached in tab Import_data,column T i would like to verify if every size exists in the Mastergrids file.
i managed to write the formula but it is only for the first size in the cell. Also, my idea was to leave it blank in case of Match,and only populate the cell in case of Mismatch.

is there anyone who has any idea on how to do it?

Thanks everyone for the support