Transfer data to and from userform

Hi all, I was wondering if someone could offer coding advice to solve some problems for an excel novice.

I have attached a mock up sheet for demonstration purposes. This spread sheet is to be designed to be as simplistic as possible; the entire interface will be form based with no direct access to any cell data. The attached mock up contains three forms; a front end prompt on load, one form for order entry and one form for editing an existing order. I had considered dropping the third user form entirely and just re-use the order entry form for both order entry and modifying an order as it would appear more efficient but for this mock up, its three forms.

My problem is 3 fold. Whilst User form 2 writes to worksheet cells correctly and via user form 3, I can retrieve the relevant cell information, the problem is that any changes I make using user form 3 will create a new entry on the worksheet, when what I want is for it to just modify the relevant order information; also, how best could I implement an alpha numeric order number search lookup and lastly when an order is written to the sheet, how best to simultaneously apply formatting to the data?

Your help is much appreciated.