How to get -ve from +ve calculation?
 

I need to calculate margin required for trading,
if there is 1 buy & 1 sell, I need result as 1 & -1,
for example:

cell
A7 buy B7 1
A9 buy B9 1
A10 sell B10 2

So far my formula in cell H10 is :
=IF(OR(A10="buy",A10="sell"),ROUND(((H$3*B10)*1000 *0.05)*C10,2)," ")

how do I make it work to give me a -ve result? please help.

Thanks.
Mukesh