I do this all of the time. If you do it this way, it will work no matter how long your list gets on sheet 2.
Let's call sheet 1 "Orders" and sheet 2 "Reference". On the "Reference" sheet, you need to define a name.
First, make sure your field names start at cell A1 on the "Reference sheet", and that you only use one row for the field names. Your data needs to start on row A2.
Next, go to:
Insert
Name
Define
In the field located under "Names in Workbook" let's give it a name like "List"
In the field at the bottom (under "refers to

, type copy and paste this equation:
=Offset('Reference'!$A$1,0,0,COUNTA('Reference'!$A:$A),7)
This formula makes it so the entire dataset can go on and on (up to excel's row limit). The "7" at the end indicates 7 columns (if you end up with 8 columns, change the 7 to 8).
On the "Orders" sheet (sheet 1), I am going to assume that your field names are on ROW 1, so I'll start putting the data on ROW 2. Have column A2 be the place where you put the job number. In B2, type the following:
=If(ISERROR(Vlookup(A2,List,2,False)),"Not Listed",Vlookup(A2,List,2,False))
That part after the word "List" (in this case the 2) says lookup cell A2, Refer to the "List" on the "Reference" sheet and return column 2. The ISERROR part basically makes it so that if you input a job order that doesn't exist on the "Reference" sheet, it will respond with "Not Listed"; therefore telling you that you need to go to the "Reference" sheet and add it.
Use the same equation for the other columns on the "Orders" Sheet, but for column C you would put a 3 instead of 2 in both part of the equation (the part after the word "List,". The same goes for the others (D=4,E=5,F=6,G=7).
Example - for column C
=If(ISERROR(Vlookup(A2,List,3,False)),"Not Listed",Vlookup(A2,List,3,False))
Once you have them all in place,highlight B2 through G2 (if you are using 7 columns), and drag all the way down the spreadsheet (as many rows as you need). Of course, don't drag column A since it will be the area you put the job number.
I know this seems detailed, and a bit long, but it is something that has worked for me very well. The best part is that you don't have to do any adjusting of your "Reference" sheet or other formulas. Once you set it up, you can go all the way to the 65,000+ lines that Excel has to offer.
Let me know how it worked.