Keep a running tally and file a SAR when it crosses the $25,000 threshold.
You can also keep track of where the checks are being passed. If a pattern develops you can consider contacting the depositary bank(s) to give them a heads up (if they haven't awakened to the facts themselves). Also, the pattern(s) should be discussed in your SAR narrative, if filed.
Think about filing information on the checks -- especially if trends are seen -- with BOL
CrimeDex.