Shift Schedule

Hi all

I am new to this site, I did do a search for what I want to do, but ones i saw were not helpful.

Also I have not used excel for about 10yrs now, so I am a bit rusty.
What I want to create is spreadsheet that automatically puts shifts in for other workers, once one employees shifts have been put in. There are 7 employees, 2 shifts, Night and Day. 2 employees have to be on each shift... I have started the spreadsheet, put in the drop down list box, but after that I am a bit lost. I have tried to find things out, but seem to be getting a bit lost, do I have to use formulas or macros to do what I need too....any help on this will be greatly appreciated and I do apologise if this has been asked before....