: I am attempting to reconstruct a DB i wrote in MSAccess 2 years ago, only this time with filemaker. One field requires a unique ID which consists of 3 uppercase letters and 4 numbers eg ABC1234. How can I restrict the input to only accept this format? Any help would be greatly appreciated.

Try a validation by calculation:

Let ( 

mask = Substitute ( Yourfield ;  

[ "0" ; "#" ] ; [ "1" ; "#" ] ; [ "2" ; "#" ] ; [ "3" ; "#" ] ; [ "4" ; "#" ] ; [ "5" ; "#" ] ; [ "6" ; "#" ] ; [ "7" ; "#" ] ; [ "8" ; "#" ] ; [ "9" ; "#" ] ; 

[ "A" ; "@" ] ; [ "B" ; "@" ] ; [ "C" ; "@" ] ; [ "D" ; "@" ] ; [ "E" ; "@" ] ; [ "F" ; "@" ] ; [ "G" ; "@" ] ; [ "H" ; "@" ] ; [ "I" ; "@" ] ; [ "J" ; "@" ] ; [ "K" ; "@" ] ; [ "L" ; "@" ] ; [ "M" ; "@" ] ; [ "N" ; "@" ] ; [ "O" ; "@" ] ; [ "P" ; "@" ] ; [ "Q" ; "@" ] ; [ "R" ; "@" ] ; [ "S" ; "@" ] ; [ "T" ; "@" ] ; [ "U" ; "@" ] ; [ "V" ; "@" ] ; [ "W" ; "@" ] ; [ "X" ; "@" ] ; [ "Y" ; "@" ] ; [ "Z" ; "@" ] 

) 

;

Exact ( mask ; "@@@####" )

)