Assuming the cell to be tested is A1, then highlight all the cells in
row 1 and click Format | Conditional Formatting. Choose Formula Is
rather than Cell Contents and enter this formula:

$A10

then choose what format you want - foreground colour or background
(patterns tab) colour - then OK.

If you want to apply this format to several rows, highlight the same
cells, click Format Painter, then highlight the cells on other rows.

Hope this helps.

Pete