Check cells for contents

Hi

I am trying to create code that checks 4 cells for content and if any of the cells don't have content a message tells of this fact.

Eg. Cells A4, A6, A10 and A11 must contain either text or time (manually input) if either one of the cells has not been populated a message is shown!

I need this to highlight every row on worksheet so if cell B4 is poppulated so B6, B10 and B11 must be completed also etc.

Thanks

Cheelie