The cool thing is a filter is the same as an action, only it returns a value, so just set it up as a filter instead:
add_filter( 'myplugin_clean_logs', array( 'MyPlugin_Logs', 'clean_logs' ) );
Then something like:
$affected_rows="";
$affected_rows = apply_filters( 'myplugin_clean_logs', $affected_rows );
should pass $affected_rows
to clean_logs()
(and whatever other functions you may have hooked to myplugin_clean_logs
) and assign the return value back to $affected_rows
.