Would it suit their purpose if, having done the <Ctrl-F>, they then hit <Shift-Space>? That selects the entire row, which highlights it though not in a color you can control.

If you want a more noticeable color, all that occurs to me is a VBA solution: Set it up on their machines so that <Ctrl-F> triggers a VBA macro rather than the Find function (can we do that?). The macro acts like Find in that it receives the string and locates it in the worksheet, but then highlights the entire row in some bright color.