handling duplicate entry

I am using php & mssql server in devloping scheduling and booking system.
I have a problem when i come to handle duplicate entry in mssql server
I used to handle this in mysql using mysql_errno() for duplicate entry.. but in mssql it gives a message instead. And there is no such mssql_errorno() function in mssql…
I was told to use stored procedure, but i have no idea ho to do that and to invoke sp function in php

i really do not like to handle that by checking the word exist or not,i think it might slow the db when it grows.
here is my table:
table name: working_days
fields:
wd_date(pk),wd_year,wd_emp_id(fk),wd_shift_id(fk),wd_on_off
all of them of type int and the field wd_date is storing timestamp value

Thanks

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