You certainly can improve upon it.
You do not need the brackets around cell references, $W$36 instead of ($W$36)
You don't need to test separately for >0 and =0, IF(C$12>0,($W34),IF(C$12=0,($W34), you can do it in one step, IF(C$12>=0,$W34
If you test for the numbers to finally get to >=0, any other result must be less than 0, IF(C$12>0,($W34),IF(C$12=0,($W34),IF(C$12<0,"", so no need to test, it defaults like so IF(C$12>=0,""
In summary, all you need is
=IF(C$12>35,$W$36,IF(C$12>17,$W$35,IF(C$12>=0,$W$34,"")))
BTW, although Office 95 only allow 7 nested statements, this final formula would work then as well.