adding a date to a row in a portal

Hi

I am using FM Quickstart V17 and have been adjusting the invoice part to work for invoicing rates of things rather then a product.

I want it so I can add a date to the added rate ( in the invoice tab), when you click on add rate you can select a rate. but what I need to be able to do is assign a date to that rate so they know what days worked. I tried adding in a date field and that didn't work, then I tried adjusting the SKU that was already there into a drop down calender, but as soon as you adjust and select a date, the whole row disappears. Am I trying to do something that is not possible? if I am not could someone guide me to how I might achieve this. thanks.

Sarah 

no passwords needed. 

Invoice_database.fmp12