Conditional formula with an if statement

[Tyler2006]

I am wanting to create a "envilope" budget sheet and have ran into a problem.
What I am trying to do is make everything in Column B all negative unless I
put a figure in Column A, which would make the Column B Positive.
Example:

Column A Column B
Deposit Car
(nothing here) $50 (this will show up negative)
$500 $500 (This figure will show up positive)


I want to be able to add numbers in both column A and B but reflect the
appropriate sign as an expense (with nothing being added into deposits) or as
income, when I deposit something in that account.

So when I sum up this column, it will equal $450 left in the car envilope.
I am struggling to figure out the conditional if statement, or am I looking
at this wrong and should place this in Macros?

 

[Don Guillett]

try this
=if(len(trim(a3))>0,a3,-50)