Try loading the values for the field you're comparing into a multi-valued list. Then you can compare the adjacent value without a join.
stats list(conc) as conc by Menu_Id DESCRIPTION APPLICATION CO_CODE DATE conc1 | eval yes = if(match(mvjoin(conc, " "), "conc_day1_value (conc_day2_value){1,2}?"), "True", "False") | search yes=True
What this does is reads the list and looks for the change in value you specify (in bold) between 1-2 times and tags the event with a field "yes" with a value "True" or "False". You'll probably need to change the fields here a bit but the logic should render what you're looking for.
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