Hi,
As per my knowledge there is no direct way of achieving this, but you can do it by adding logic in Interface (BLS).
Below is the logic :
Suppose you have two interfaces A and B, define a Persistent or Inline variable(P) in A which will update the variable with Flat as "X". Now in interface B, write a condition if P=="X" then execute else terminate.
Also, dont forget to set the flag value as Blank once B executed successfully.
Hope this help .
Thanks
Shashank