OPOS Coupon Generator

I need an application developed which will monitor and inspect print jobs sent to a particular OPOS printer (Epson or Samsung OPOS drivers currently in use) and upon finding a user defined string, automatically generate a subsequent print job. The specific application will be a Point of Sale coupon generation application where we would like one or more coupons (printed on receipt printer) generated if certain information is presented on the customers bill. For example we may determine that any receipt with a total more than $200.00 should generate a simple entry form automatically. In this case we would determine a search string to look at the total on the customer bill and if it is more than $200 automatically print an entry form. Another example would be that if a particular item exists on the customer receipt, then a discount coupon for a future purchase should be printed. The extra coupon to be printed will be text based but we should be able to include a include a logo at the top of the coupon. This is the same logo which currently prints on customer receipts and is in jpg format. Reliability of the application is very important as this is for use in a high volume retail application. If possible application should not interfere with original OPOS print functionality such that there is no chance of receipts not printing.