creating a general journal line while posting a rental order in Microsoft Dynamics Nav 2009

Question

I have a custom modification for a customer where they want to keep track of a specific amount while posting a rental order. The way I have it written is when the posted rental line is being generated, create a line in the General Journal Line table to keep track of that amount for each line, but I keep getting this error message where it's telling me to use COMMIT but I don't want to use COMMIT. Here is the error message: