Auto filling a form with conditions

Hi,
I want the information I enter in worksheet 1 to automatically be loaded in the form on worksheet 2. The problem is: I don't want worksheet 2 to auto fill information on a PO who's status is "Not Done" and I don't want there to be any blanks in my form on worksheet 2. I added an attached basic file in excel 2003 which may help also since the margins on the example below are confusing.

Worksheet 1:

A B C D
1 PO Number Status Ship Date Tracking Number
2 101 Not Done N/A N/A
3 102 Done 10-31-2012 1234567
4 103 Not Done N/A N/A
5 104 Done 11-5-2012 7654321

Worksheet 2:

A B C
1 PO Number Ship Date Tracking Number
Formula Needed: =LOOKUP(A2,SHEET1!A:A,SHEET1!C:C =LOOKUP(A2,SHEET1!A:A,SHEET1!D:D
In A1 of Worksheet 2 I want
The PO number (Column A) in
worksheet 1 B2 IF the status is
"Done". If the status is "Not Done",
I want to go to the next PO number
that is "Done" and put that PO number
in this cell.