Use of the "Force Monthly Statement' option on the member's MASTER record will allow for member to receive a monthly statement instead of the quarterly/annual statement they may qualify for based on your overall statement configuration settings. Remember that this is intended to be used only in rare occasions where there are exceptions to your rules. If you find that your staff is setting this flag on frequently, you might need to (a) revisit your general configuration settings or (b) be prepared for an increase in your statement printing costs!
This flag is controlled via Tool #15 "Update Membership Information."