Cropped Moving 2D Texture

I’m only two days old to OpenGL and I’m really excited about the possibilities. I have resolved to learn it to the best of my ability.

I am a Java guy with some basic knowledge of C++, however, the IDE settings always get me in VC++.

My first openGL project is a moving map of the world.
Here is how I have set it up. There is an external program that calibrates an image and maps out the image pixels to the corresponding real world latitude & longitude.

My VB.Net Program displays part of the map in a small window with a crosshair (or an aircraft) centered over the real world coordinates entered.

It works pretty well in VB, but I need to implement the same in OpenGL.
What I basically need is a way to display only part of a larger image, based on the pixels boundaries I enter.

I’ve searched on cropping textures, but I don’t think this is the efficient way to do it.

I’ve attached a screen shot of the VB display box.

Any help would be much appreciated.