Compare two list

Hi,

I want do the next:

I go to website and take all links I see. Well If I do today I find 50 link, thats work good. I save this links in a list and do something with this.

The problem is that when I return tomorrow I find 60 links, 50 I take yestherday and 10 new link. I only want save new links.

I think and think, I know I can download all links again and later delete duplicate, but how I can say to my template do something with only new links I found?

Thats it.

Thanks for read.

Now I read and don`t understand some comands but I go to fight with software before asking again.

Thanks for your help

oK, I have variable {-variable-linkfound-}

I can have nothing or htp:/....

How I write in logical if, if {-variable.linkfound-} are empey do something Else do other thing?