how do i tell deck box my card is foil wile im typing in my deck?

Decks don't have specific, actual cards in them. They are just a list of cards. Does that make sense?

That being said I believe the Deckbox team has something that they are working on which will make it so you can add specific, real cards to decks.

how do i know how much my deck is rely worth?

"Worth" has a couple different meanings: Trade value and Market value. How much you could trade the deck for and how much you could sell the deck for.

Trade value is easy to explain. That is the number shown in the deck page. This is the total of the average price of each of the cards in the deck. Take your sliver deck as an example. Underneath the name of the deck it says "Approximate deck value: $371.71." That is the trade value of the deck.

Market value is more difficult to figure out. Generally, take the cheapest copy of all of the cards individually on TCGplayer.com and cut that by 10 or 20 percent.