Hi Devs!, Creating custom lookup is common in Dynamics AX. Similarly, we are having requirement to create custom lookup but it would have "Sum "aggregate function used along with grouping. There are parallel approach also but in many scenario it wont working due to grouping. Parallel Approach but in many scenario it will not working due to grouping (at the end) Step #1 : Form --> DataSource --> fields--> Method--> Override Lookup method Step # 2: Create a table which we will be using as a temporary table. This table will be having same fields that you want within lookups. Step # 3 : Code Data within Lookup table need to be deleted so it depends on the scenario where you need to perform delete operation. I delete it whenever new line is created. Final Result : Sum Aggregate function used on SoldQty. Parallel Approach :