Roster Day/Night Shift

I have been working on my own roster over time with some help already from this forum and am stuck on one thing. I can choose from a drop down list which employee I want to do a shift after this the name no longer shows for that day only. The following day the name returns which is great. Once the name is chosen it auto calculates man hours on second sheet.

My question is this, is there any way for the drop down list to not show the employees who were on the Night shift in the followings days Day Shift and vice versa?

I hope I have explained that properly I would appreciate any help. I have attached a copy of the roster to help.

Cheers