no.

if u hv the credit limit, it will be done if the price comes.

then, u get the statement... need to top up to pcik up, or sell before contra days, or they will force sell for you.
such questions about basic procedures, the remisier/broker should have told u.

if not, u should call and ask - that's part of the brokerage u pay!

there are diff types of accounts, diff rules.