flag may be implemented so that it may not be changed back to 0 once it has been changed to 1 when irregular activity has been found an email may be sent to the seller and or bidder at an address associated with the user identifier of the seller and or bidder the seller and or bidder may further be banned from participation on the auction site by using the pointer linking to the user table to update a u201c irregular_user u201d or similar field in the user record of the seller and or bidder the irregular flag 301 304 in fig3 a and 3 b may be updated based on another price based value such as a price based fee 330 for example an auction site 10 may charge sellers fees based on the selling price of an item thus the auction site may use the formula for determining fees to determine a threshold fee for monitoring irregular activity in fig3 a and 3 b the threshold fee for the category computers for example may be 200 based on a threshold price of 15 000 in another embodiment the threshold fee may be simply the average fee plus a set amount such as 300 for example thus if the average fee for computers is 40 for example then the threshold fee may be 340 many other algorithms may be used to determine a threshold price based value such as a threshold price or threshold price based fee the threshold price based value may also be determined based on the currency of the transaction the category of the transaction or the geographic location of the transaction for example a table may be used to determine threshold prices for items where the rows of the table represent the categories of.