Check for repeated input

Hi,

This is a bit of a long post for my first but here goes...

I have created a spreadsheet for which I want to check when entering data into a column whether this data has been repeated elsewhere in the worksheet and on other worksheets. If it is repeated then a warning should be shown with options to continue or cancel. I can do this easily for a single worksheet using data validation but cannot think of how this can be done between workbooks especially when the number of workbooks can vary.

If I can manage to sort that then I'd like to offer an option to copy the data from the row where the original reference was placed. As a further feature I would then like to be able to update all rows for a particular reference.

eg 01 Data X Data Y Data Z
02 Data X Data Y Data Z
03 Data X Data Y Data Z
02 As 02 is entered option to paste data from line 02 above and then track data between these lines to ensure that it's always the same.

I know there's a lot to do there but any advice on any of the above would be hugely appreciated.

Many thanks in advance.

Any ideas anyone?

I guess that's a no then. Any help at all would very much appreciated as it's driving me mad; I just can't figure out how to do any of this!! Please help!!