How we can find out Relationship of two system tables using database diagram in system databases

i have to schedule backup of particular schema objects, using sql server agent jobs. in database there is five schema like schema [a] [a].tbl_a -- Table [a].usp_a --Procedures [a].fn_a -- udf schema[b] [b].tbl_b --Table [b].usp_b --Procedures [b].fn_b --udf where [a] and [b] are the schemas. now i have to schedule full backup of only "[a]" schema objects. And there is only one file group(Primary) for database. using sql server agent job,is it possible or not?