Auto Generate Work Order

Hi, I am a newbie to this forum. I really need help with using macros to automatically generate a work order number for document requests. This is what I want to happen to the spreadsheet. Every time I enter the "Date In" I want a work order number generated. Say if 2 task came in for the same day the last number will increase by 1 for the same day like the example below. I hope my explanation is clear. Please let me know if otherwise. I have attached the table for reference also.

Date In Work Order#
30/03/2016 WO# 3003161
30/03/2016 WO# 3003162
31/03/2016 WO# 3103161
01/04/2016 WO# 0104161
04/04/2016 WO# 0404161


Thank you and greatly appreciate your help.

Daych