exclude contextual term from block

Hi All,
I have a problem that I can't solve:
I have a view showing all nodes tagged by a specific taxonomy term. This term is passed as an argument (contextual filter) This wiew is working properly.
I created a view block that shows all taxonomy term of that vocabulary, working properly.
Now I have to exclude from thate block the term that is being viewed (the term that's in the url, the argument). But in contextual filter I cannot find anything useful.
The only i can achieve is to show in the block just the term in the argument, passing it as a default value with a taxonomy term contextual filter.
What i need is exactly the opposite. Can I negate this filter? Or there's some other method to achieve this?

Thanks in advance

Should the post's category be a feature request?

Edubacco