As a member of an organization, you have a right to vote on motions under consideration according to Robert's Rules and basic good practice. Voting is a right that comes with some responsibilities, as well.
It's your duty to vote when you have an opinion about a matter being decided. By failing to vote, you allow others to make the decision, which is the same as having voted for the prevailing side. Whether you vote or not, you're still in some way responsible for the decision that's made.
On the other hand, you can't be forced to vote, and in fact, should not vote in certain situations. According to Robert's Rules, you should abstain from voting whenever you have an interest in the outcome that directly affects you personally (or monetarily) in a manner not shared by the other members of your group. The key here is that the other members don't share your interest. For example, it's certainly okay for you to vote in favor of, say, holding a banquet, even though you have a direct personal interest. You benefit from having the association buy your dinner. But so does everybody else. However, if the motion decides whether to give your company the catering contract, good form compels you to abstain from voting.
Just to be clear, the abstention rule is a should rule. Just as you can't be forced to vote, you can't actually be compelled not to vote. As a voting member, you can vote to swing the contract your way, but it's bad form if you do.
The rule that you should abstain from voting on matters of direct personal interest to you doesn't apply if you're nominated for office. If your status as a member makes you eligible for the office, you're entitled to benefit from a vote as any other member would. So go ahead and vote for yourself, if you want to.
When the group has moved on from the debate stage and voting is underway, you're not permitted to get a little debate in edgewise under the guise of explaining your vote. The right of free speech stops when the voting starts.
When voting by any method except by ballot, if the result of a vote has been declared, you can change your vote, but only with the unanimous consent of the assembly without debate. Otherwise, it's too late. However, you have an absolute right to change your (nonballot) vote at any time up until the result is announced.
No matter how many constituencies you may represent at the convention, or how many offices you hold, you have only one vote in the assembly of which you are a member. Secretary and treasurer may be two offices on the board, but even if you're serving in both offices, you don't get to vote twice. The rule of one person having only one vote is a fundamental principle of parliamentary law.
All questions related to the manner and methods of voting are within the control of your group except as your bylaws may dictate. Through the use of incidental motions related to voting and the polls, your group remains in control of its own voting procedures.