Dynamic setting of data source

Hi, Thank you for your quick reply with solutions in this context. While I will take a closer look into your suggestions, I would also like to add more clarity to my query. I am not trying to create a list for the dropdown box. I am using the dropdown box with the field type of 'item' which allows me to pick an item and assign it to the same field. For example, let's say I have the following items on a grid with four columns (Name of the attribute, Value as a string value, Data type, Data source if applicable) 'A'    <value>    'item'    'user' 'B'      <value>   'string' 'C'      <value>   'item'     'order' So, when the user selects 'Show instance' on Row A, the form would have a dropdown box of type 'item' and data source 'user' (which is an item type). And when the user selects  'Show instance' on Row C, the form would have a dropdown box of type 'item' and data source 'order' (which is an item type). Many thanks for your support. Alexis.