SQL & PL/SQL :: Write A Trigger To Validate V_status For Each ID

I want to write a trigger to validate the v_status for each ID. below is the example

SEQ_NO ID V_STATUS

11 C
21 C
31 F
42 C
52 F
63 C
7 3 F
8 3 C

For each unique id there will be only one F .. if some one tries to update the 2nd F to the same ID it will show the error message that ID is already F.

SEQ_NO ID V_STATUS

11 C
21 C
31 F
42 C
52 F
63 C
7 3 F
8 3 F