if you added a table through AET, you can use CRM_ORDER_MAINTAIN. there are two enhancement parameters.
Please create the activity from web ui and enter values in your AET AB. put a break point in CRM ORDER MAINTAIN
you will come to know how to fill these values.
one more thing is place break point also in the FM you intend use. if it tirggers, then you will come to know how use the extension parameter.
I have already used CRM ORDER MAINTAIN to main the values.
hope it helps.