Ok, seems like I was confused. Now I closed my foxpro, restarted everything and made some others tests.
I think I was setting the wrong parameter no_hist instead of vno_hist, and forgot to use clear all.
Everything is now fine. I think the problem was the filter that had the same parameter name as one of the view's field.
Thank you for the help and I apologize for the time you may have waisted with me.

>>When I try it in the command window it also appears empty. It's like it can't find the variable's content.
>>
>>
>>This one ask me for the parameter in an input box and works well
>>*
>>USE "viewname"
>>*
>>
>>
>>
>>This one does'nt ask me for a parameter(so I guess it "sees" the variable) but it gives me an empty view
>>*
>>vno_hist= 1299
>>USE "viewname"
>>*
>
>It doesn't see the variable. If you want to use variable, use ?n1 in View designer. If you don't use '?', view can understand this as constant. Anyway, don't try to cheat View Designer, it's 'good enough' to cheat people itself.