yogi_Extracting And Rearranging Data From Single And Multiple Sheets

Yogi Anand, D.Eng, P.E.                                         Google Spreadsheet                            www.energyefficientbuild.com

canned.meat.eater said:
The desktop sheet contains data about the desktop, user, etc, but most importantly it contains the serial numbers of the monitors that are used with it.
"desktops"
A B C D
SN: User: Used w/:
1234 john abcd efgh
5678 jane ijkl mnop

On the monitors sheet, I want to populate information in this sheet based on the information on the desktops sheet, but it will look something like this:
"monitors"
A B C
SN: Used w/: Contract #:
abcd (???1234) ab12
efgh (???1234) ab12
ijkl (???5678) cd34
mnop (???5678) ab12

To try to put it into words, I need to populate monitors!:B2 with the value of desktops!Ax by finding value of monitors!B1 in either desktops!C or desktops!D...

I realize that it might be easiest to put all the info on one sheet, but for ease of finding, reading, printing I would like to seperate the data out, hopefully without having to input it multiple time and trying to keep track of it.

This might be easy, but I haven't been able to figure it out. And I might not have done a great job explaining what I need to do...sorry.
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Well, I requested canned.meat.eater to share his spreadsheet ... to which I haved added thr following sheets

yogi_monitor1
yogi_monitor2
yogi_DesktopsAndLaptops
yogi_monitor3