One value allowed once in row using a list

[EA-ATC]

I am in need of a formula that will allow a value in a drop down list to be used only once in a row.
List located D200-D876
So row D10 through J10 will all use this list (D200:D876) but the value cannot be allowed to duplicate within the row. I will need to repeat this function for each row D11:J11, D12:J12, etc.

I want the boxes to remain blank if nothing has been selected in the drop down. (D200 is a blank) Think of it as 600+ different names and you can only be in one place at a time (row 10). The next row (11) is a new day and you can be somewhere else.

I only want to use a formula, if it won't work that way then I cannot do it. Excel 2010

Thanks for taking the time to read this.

 

[sijpie]

http://www.contextures.com/xlDataVal03.html

 

[EA-ATC]

Thanks! This is exactly what I have been searching for.