Other Cells to be associated with data validation lists

I am setting up a spreadsheet that simplifys some data entry.

The aim is to have a cell with a drop-down box where you can select a persons name from a list, which has been entered on a separate excel sheet. By selecting a certain name, the cell directly on its right will be altered accordingly by the next cell that has been entered on the second excel sheet.

For example say cell A1 is the drop-down box and Dave is selected, Cell B1 will change to A
If cell A1 is selected as Steve, cell B1 will change to B.

I want to know if it is possible to have a have this set up where the use of the drop down box will automatically update the cell next to it accordingly (in this case A or B).

I hope I have made myself clear enough.

Thanks in advance.