|If there is some sort of "pattern" to the selected/highlighted cells then it could be done with the following code. The pattern I'm assuming here is that the cell you want highlighted is 7 columns away. i.e. A - H|
You will also lose the use of one cell as it is required to store the highligthed cell's address so it can turn off the highlighting when you mkae your next selection.
Try this code and if it's even close, let me know what else you need.
Private Sub Worksheet_SelectionChange(ByVal target As Range)
On Error Resume Next
'Get address to reset highlighting
oldTarget = Range("A1")
Range(oldTarget).Interior.ColorIndex = xlNone
'Highlight cell 7 columns to the right
target.Offset(0, 7).Interior.ColorIndex = 6
'Store highlighted cell address for use next time
Range("A1") = target.Offset(0, 7).Address