I do not know about condition formatting when mailmerge. But why do not split your list following the rules and create a mailmerge as many times as needed?

>I have a list of address associated to a unique identifier number. The mail merge template is set to print all these address in the label format on both sides of the paper.
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>Problem :- Require to force the labels to print on a new page when the unique identifier changes. Also instead of printing on the other side of the paper the labels need to start on a new sheet of paper every time the unique identifier changes.
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>How can I do this?
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>Your help is very much appreciated. Thank you.
>Neetu Kumar