Conditional formatting across worksheets

Sorry for posting what has probably been asked a thousand times but need help with this and can't seem to find the solution trawling through the forum.

I have a workbook working as a year planner. Sheet 1 is the entire year, a month to a row and a column per day in that month.

Each week then has a worksheet to input data for what is booked in that day, client name, location etc. Obviously there is a few of these!

What I am trying to do is if I enter a booking for 1st Jan on the week worksheet with it's relevant detail (the actvity being in cell A4), the cell for 1st Jan on the year sheet (B1) colours as per conditional formatting so I can see which days have a booking across a year.

I already have in the year worksheet a hyperlink that leads to the relevant day on the week worksheet for each date in the year.

Can anyone please tell me how to make 'Year'!B1 colour when I type into 'Jan 1-7'!A4?

Thanks everyone

Thanks for that. I don't know how to name a range though. Can you explain that please?

Martin, you Sir are a star. Thank you very much. Good description and very helpful, sorted my year planner nicely.

Thanks again