how to creat code with VB to calculate dat ot Year(2012)

I would like to know how to write vb code about this:
My question is
1. a combobox to selct month
2. a textbox to input Day
3. a label to display Day of Year(2012)
4. and click add the button to calculate and show the result

For example:
Feb. 14 is : the 45th day of this year.

I'm new and still learning.

Thank you so much for your help.