one of the documented procedures in this installation of the ACS
ad_table_same   varname
What it does:
Called from inside ad_table. returns true if the variable has same value as on the previous row. Always false for 1st row.
Defined in: /web/philip/packages/acs-core/table-display-procs.tcl

Source code:

    if { [uplevel set Tcount]
         && [uplevel string compare \$$varname \$P$varname] == 0} {
        return 1
    } else {
        return 0