Decrypt concat lookup

Hello,
I have the following situation:

Table 1:
Table1.ID
Table1.LastName
Table1.FirstName
Table1.MiddleName

In Table 1 the LastName, FirstName and MiddleName are AES encrypted in the database.

Table 2:
Table2.ID
Table2.role
Table2.person

I want to add a row in Table 2, via a lookupwizzard.
The linkfield is ID, but the displayfield should be: concat(LastName,', ',FirstName,' ',MiddleName)

I just can't figure out where and jow to perform the decrypt.
Or how this could be managed easily.

Any tips or an example would be much appreciated.