Conditional format to check for entry presence in multiple worksheets

I have a spreadsheet with 13 tabs, Template and each month of the year, column A on each sheet is for the repair order number and what I need is a way to alert me if an R.O. number I input is already listed above itself or on any of the other sheets thereby avoiding repeating myself to the accounting department. I have been trying to set up a conditional format based on some of the post answers I have read but I haven't hit on the one that will work both for all the other sheets and the one I'm on also, seems that if I input the number into the name range on the sheet I'm working, it sees itself and therefore it adapts the cf set up for the alert so all the numbers on that sheet are lit up. Can anybody give me an idea that will work??