Depending on the one DFF value, another DFF will be enabled or disabled

The following concept is also applicable for report parameters 

Here in this case if the AT1 value is ‘Y’ then AT3,AT4,AT5 will be enabled.

If ‘N’ then it will be disabled

MT1 is independent value set.

MT2 is Translated independent.

Default Type: ‘SQL Statement’, 

Default Vale: SELECT DECODE(:$FLEX$.MT1,'Y','Y',NULL) FROM DUAL

Display property of AT2 is null

MT3 and MT4 are table dependent value set.