Subtracting Time Zone for Universal Time and Date

[Pal]

I am trying to adjust a user inputted time, date and Time Zone to Universal
time.
Date: C2
Local Time: C3
Time Zone: C4

But the problem is subtracting time.
So if I have

02/01/2004
5:00:00
-6

I need my new date and time to read: 01/31/2004 23:00:00
And if the Zone is +20 then the new date would be: 02/02/004 1:00:00

I have a function that calls Year, Month, Date, Hours, Min, Sec to get the
Julian Date.

I tried combining the date and time into 1 cell "dd:mm:yy hh:mm:ss" and
doing the math but I had no luck
Is there an easy way to achieve this goal?
Thanks

 

[Earl Kiosterud]

Pal,

It will require a macro, or some judicious circular references (not
recommended in this situation) to actually change the date and time in C2
and C3 as a function of the time zone in C4. Better is to put the new
date/time in a separate cell somewhere:

=C2+C3+C4/24