have finally got this to behave with what I think is a valid condition (not just ConditionTrue) - anyway it will now switch on and off according to setting of scroll counter if required

Code:
declare_counter scroll
set_counter scroll 0

;;use this version to apply to all settlements
;monitor_event ScrollOpened ScrollOpened loot_settlement_scroll
;   set_counter scroll 1
;end_monitor

;use this version for named settlement
monitor_event GeneralCaptureSettlement FactionType greek_cities
   and SettlementName Athens
   set_counter scroll 1
end_monitor

monitor_conditions I_LocalFaction greek_cities
   if I_CompareCounter scroll = 1
	while I_CompareCounter scroll = 1
	disable_ui loot_settlement_extermintate_button
	end_while
   end_if
end_monitor

monitor_event ButtonPressed ButtonPressed loot_settlement_occupy_button
	enable_entire_ui
   	set_counter scroll 0
end_monitor

monitor_event ButtonPressed ButtonPressed loot_settlement_enslave_button
	enable_entire_ui
   	set_counter scroll 0
end_monitor
it needs enable_entire_ui when either of the available loot buttons is pressed to get it to switch off properly - trying to use ScrollClosed or enable_ui loot_settlement_extermintate_button doesn't work but above seems to