I need to apply conditional formatting to some cells. It's quite easy using
the conditinal formatting function, but I need to use code.

Column A will be changing, and depending on if there is a value or not, I
need cells on that particular row to change color.
For example, if A1 has a value, and cells A3, A5, A7 are blank, they should
change color and a message should display. Once values are input in each cell
(A3,A5,A7), each cell should return to their original color.
Thanks in advance for your help.