|So is it your question that is urgent or do you want to mark a cell as urgent?|
Since putting URGENT in a subject line might actually cause us to respond slower, I'll be nice and assume the URGENT refers to the formatting you are asking about.
Assuming you want this formatting applied to Column A, try this:
Highlight Column A
Pull down Format...Conditional Formatting
Pull down Formula is... and paste this in:
Format button...Patterns tab...Red
The process is the same for any range, just change the A1 to match the cell(s) you want formatted.