Data validation - static values PLUS dynamic list possible in same cell?

[lemeister]

I am looking to create a data validation list that has one static value ("***ALL***") and also a dynamic list. Is this possible?

I have tried the follwing forumula but it returns an error:
="***ALL***",OFFSET(DataStart_UniqueCombos,MATCH($C$6,Tables!$B$6:$B$219,0),2,$F$7)

The dynamic list works fine on its own (it is a cascading lookup dependent on another cell's value), I just want be the static value appearing at the top of every dynamic list that gets generated.

Any help appreciated.