I just recently posted with a question about a formula to not be able to
schedule an Employee if they requested a day off, and it worked great. Thanks
to T. Valko.

They gave me the formula =MATCH(A3,B$5:B$23,0) to assist on my question.

I was wondering if I need to use the same basic formula for my next problem
area. I have tried using it, but to no prevail.

Question:
In cell B4:B23 I have a list of all the Employees for that DAY SHIFT and
what times they come in, as well the position they work. (a drop down menu is
in use to select employee names)
In cell H4:H23 I also have a list of all the employees for that NIGHT
SHIFT what times they come in, as well as position they work. (a drop down
menu is in use to select employee names)

I would like to know if there is a way to prevent a user from scheduleing
the same employee twice in a day in two different positions. We have had
problems in the past where the Manager scheduled an employee twice in the
same day, and we were left short handed. Of course we have some employees
work between shifts so they are oviously going to be on both shifts; as well
as splits. (no problem there is it shows that we have an employee scheduled
twice in that sense).