Auto entry in a form

[Phil]

Hello,

I have a sales form, order details, that shows Product ID, quantity, Unit
Price, etc. I have a Products table, Products, that has Product ID, Stock
Level, Unit Price.

What i would like to do is automatically insert the unit price into the
sales form depending on the Product ID that is entered into the sales from.

Can anybody please explain to me how to do this ?

Thank you