Option to configure dont map to a particular target account code.

In Data Management or Data Exchange is it possible to define negative mapping "Not to map to a particular target coa code"

For eg
For Target Custom 1 mapping
I DONOT want to map any balance sheet account[source] in combination with department in Custom 1 [source] to Target custom 1 as No Custom1.

one way to achieve is multi dimension mapping for custom 1.
source account - like - BS*
source custom 1 - In - select respective department codes.
Target custom 1 - No custom1
processing order - AA1

problem with this is whenever a new department code is created i have to update this particularly there when there is no pattern for departments in source system.