How to work with sub-forms?

How to work with sub-forms?

This is my 2nd email - following the previous one talking about a bug in populating data.

Here I would like to talk about my wish to be able to have a sub-form type functionality.

Take my "trade master" application as an exampe. I want to create a PO, and then, right there, open a subform to enter item numbers that belong to the PO.

If you have a way to do so, please enlighten me. It is very crucial to the implementation of my app.

Right now, my solution is that the user first enter PO. Then go to form "PO-item subtable". Select PO, select item. This two-step approach is inefficient and my users will definitely resist using it, in favor of their current excel spreadsheets

Thanks
jianqiao