Are you familiar with Windows GUI programming?
If not, you can get a start ...
HERE In POIDE... create a new Win32 GUI Project.
Then click File -> New -> Resources.
In the resulting resource page...
Right click and select New -> Dialog
Then double click on the resulting dialog to open the editor.
Now grab the edge of the dialog and enlarge it far enough that you can get the buttons out of the way.
Then move the buttons to the bottom or side so you have lots of free space.
Now on the floating dialog toolbar find the Calendar controal and click on it.
Now click on your dialog to drop the control into place.
Working with the edges, move and resize the calendar to the size you need.
Arrange any buttons you need around it...
Then it's just a matter of writing the background code for your dialog...
You can read about dialogs ...
HERE Details on the calendar control are ...
HERE Considering where you've posted this...
I would remind you this is some pretty heavy duty stuff for a beginner .
But it's not so bad if you have some experience with windows GUI programming.