This thing can go MANY different ways, depending on Bell & the Steelers working together.
Let's say the Steelers are interested in the Browns' #1 & #4. They can get those picks if Cleveland is willing to trade. Here is how you do it. You Tag Bell as non-exclusive, he goes to the Browns and works out contract numbers that he wants, agent presents the deal, Steelers agree. SIGN Bell to That contract BEFORE the Draft, and trade with Cleveland for the #1 & #4 pick. I could be wrong, but the only thing they would be on the hook for is a signing bonus. Cleveland makes it a Roster bonus payable AFTER the deal goes through, Steelers give him chump change or nothing to sign.