Well, what do you mean by a "calling?" If you mean that profession or ministry that God planned for you from before the world began then I don't believe that is a Biblical concept.
For example, Ecclesiastes 9:10 says, "Whatever your hand finds to do, do [it] with your might"
Notice it doesn't say, "Whatever God has predetermined for you to do..."
Consider also...
James 3:1 - "My brethren, let not many of you become teachers, knowing that we shall receive a stricter judgment."
If being a teacher is a calling from God then why is James implying that the decision is completely up to the individual? The answer is because it IS completely up to the individual.
If Christians become teachers because they are "called" and if God doesn't want too many to become teachers then all God would have to do is to simply not call so many to become teachers. Problem solved. But since God does not call people to become teachers, James puts the responsibility upon the individual to decide if he will be a teacher or not.
My view is that God's will for your life is like a shepherd's will for his flock. The shepherd only cares that the sheep is in the pasture. He does care which specific tuft of grass any individual sheep is grazing on. Do you want to be a professional race car driver? Then go be one. You don't need to sit around and pray to God whether or not it is His "will" for you. Since there is nothing unbiblical about being a race car driver then being a race car driver is automatically "in the pasture." You don't need to "pray about it." Just go out and "do it with all your might" (Ecc. 9:10) and "delight yourself in the Lord and He will give you the desires of your heart." (Psalm 37:4)
Too many Christians like to get all mystical when it comes to what they should do with their lives. You hear them say things like, "God opened that door for me" or "Well, I didn't pursue that job because God just 'seemed' to close the door."
What are they talking about? There are obstacles in the way of attaining anything of value. If you perceive that as some kind of a closed door, THEN KICK THE DOOR DOWN!!! Too many Christians polluted by this false doctrine of predestination let circumstances control their lives instead of creating their own circumstances.