Package A should replace Package B

[Alagarsamy]

I had package A and package B. Package A does all the functions of 
Package B and some more functions.  So installing package A  should 
replace package B. So i need to have a 'REPLACES' like directive in 
Makefile of Package A which says "package A should replace package B". 
currently I can't find 'REPLACES' directive. Is there any otherway we 
can achieve this ?

Thanks,
Alagar