Visa - Normal to Express or Rush

hi, I want to attend CISMA exhibition which is from 25th Sep to 28th Sep. I have an appointment on 19th September and want to go to China on 23rd September or 24th September. Please guide me is this possible with normal time by requesting during my appointment to issue me the visa before 23rd Sep or on 23rd Sep or I need to change to express or rush service by submitting extra fees on day of appointment? Please guide me

Shaharyar from Pakistan