Conditional Format for two different tabs in one worksheet

Hey everyone. This is my first post here and I am looking for some help.
I am a wedding photographer and I have a spreadsheet set up with a few different tabs at the bottom.
One is booked weddings, one is wedding monies, and one is potential new clients.
I have conditional formatting done on my date column in the potential client list to be bold if there are duplicate dates
but what I would love to accomplish is to have the date column in potentials turn the text red if I have a booked date from my Booked Weddings tab.
If I put a date in the potential date column and there is already a date in the booked tab date column, then the potential date would turn red.
Hope this makes sense and is possible.

Thanks for any future help.

Regards,
Toby

For identifying duplicate dates, you can use highlight duplicates option in conditional formatting. Or you can use the formula. Assuming your dates are in B column, select B2 and add this formula in conditional formatting =if(countif($B:$B,B2)>1,1,0) and make the formatting style as bold. Then copy it to all the cells in column B

For checking with booking sheet, you can use the formula =if(countif(Booked_Weddings!$B:$B,B2)>1,1,0)

Thank you for the speedy response.
I see where you are going but think I lost you. Forgive me for my lack of knowledge with Excel. I am learning more and more each day.
Here is a better elaboration on my situation.
One Worksheet for my business. I have multiple tabs at the bottom of this worksheet. The last tab is my potential clients with the date of their wedding starting in cell A3 and down from there.
I have another tab with already booked weddings by date starting in cell C3 and down. I would love for the dates in my potential tab to be formatted red if I put in a date that is already booked
from the other tab.

I am slightly familiar with conditional formatting but seemed to have lost you a bit. If figure if I tell you where my dates start and in what cell, maybe your explanation will make more sense to me.

Thanks for taking the time.

Toby

For finding duplicates, use this formula in conditional formatting of cell A3 - =if(countif($A:$A,A3)>1,1,0) and give the formatting as bold. Then copy it to other cells in A column.

For comparing with booked list (Assuming the sheet name is booked_list), use this formula in A3 =if(Countif(booked_list!$C:$C,A3)>1,1,0) and give the formatting as red colour font text. Then copy it to other cells.

Thanks for the info guys. I have tried those but it doesn't seem to be working.
I have cleared the info from the spreadsheet and attached it here as an example. I am sure it is one simple thing that is off.

Thanks for looking.

Toby

I am sorry. I forgot the fact that conditional formatting cannot check conditions outside its sheet. So, i have added a dummy column in the sheet and achieved your requirement. You can hide it later.

You've done it lwflip!!! Thanks so much. It looked similar to one that you mentioned before but looks like the only difference is the ' on either side of the tab name.
I will try copying this into my worksheet and see if I have any problems.
Thanks for all the help guys!! Much appreciated.

Cheers,
Toby

If I were you I would use the formula in the second file I posted. Using the sumproduct method might make using your file seem "laggy" if the file always has to calculate the sumproduct function. You shouldn't see this using countif.

I was just going to ask you about that...seems to really lag when I input a date.
I will try out the other one...thanks.

Second file and formula did the trick!!!

Just to help out anyone in the future looking for this formula, probably a simple one but for me I had no clue. Here it is:
=COUNTIF('2013 Booked Weddings'!$C:$C,A3)>0


Thanks for all your help lwflip and Sindhus. You guys rock.

Cheers,
Toby