LONG var, conditional invert sign

Hi all:

Now I'm starting with the new world of signed vars, and I have a type of operation that I used to do with my "signed words vars" (A word var and a flag bit var).

Example:
W as word
W_flg as bit

'I set the number 100 (positive)
W=100
'In my flag i use 1 for positive and 0 for negatives
W_flg=%1

'Conditional inversion
'Sometimes there are a config var that tell me when to invert the value of a "signed word", like multiply by -1.

Config_invert var bit

'To make the inversión I used to do...
W_flg = W_flg ^ Config_invert

My cuestion is, is there a way to do something similar with longs? the only way i can imagine is:
L as long

L=100
if config_invert=1 then L = -L

Any help will be welcome...

thanks in advance

dcorraliza