formula question in Numbers

I'm in charge of assigning lunch tables for my students at a school. I use a google program to randomize the table listing, but I do need some help.

I have all my students names in column A. Then I have each week of school in each subsequent column and the table number the student was at during that week. But now that the school year is almost over, there are a lot of columns (one for each week of the school year). I don't want any student to sit at the same table during the year. Is there a formula that can search each row and if a duplicate number pops up, it highlights the cell(s) with the duplicate numbers.

For example: a student name is in row 2. Then columns B through AC represent each week of the school year. Is there a formula that can search Row 2 for any duplicate numbers so that the student doesn't sit at the same table twice during the year.

Thank you,

Mark