Budget 17000

A C
E F-----------------COLOUMNS
Code Estimate Spending Actual Spendings Balance-----------
HEADINGS
1400 1500
G54 130
155
STU 1200 400
563 500
1000
HJ4 700
965 600
500

REQUIREMENT
I want "Macro" or "Formula" which can calculate Balance in Coloumn "F"
cells

CALCULATION METHOD SHOULD BE
As above mentioned that Budget is 17000 so in balance coloumn the
Macro or
Formula should minus first "Actula Spendings" figure from the Budget
and if there is no figure
in any cell of "Actual Spendings" coloumn then it should minus figure
of same Row cell in
"Estimate Spendings" coloumn. In other words it should always prefer
minusing figures
from "Actual Spendings" coloumn first and if there is no figure in
"Actual Spendings"
coloumn then it should minus figure from "Estimate Spendings" Coloumn.
And also if there
any code been put in "Code" coloumn cells then a text of "NOT RELATED"
should appear
in same row cell of "Balance" coloumn.

Please if you have any problem understanding above Question i have
also saved my excel file
in savefile.com where you can upload your files. Please see the link
below if you want to see the spreadsheet for more understanding.

http://www.savefile.com/files/1350632