Subdivide help

I am having a problem keeping square faces when i subdivide, they turn into triangles. Here is the situation…

Im making the hood of this car, and as you can see the bottom right portion of the hood needs to be subdivided or something to match the curve.

http://img223.imageshack.us/img223/1964/nosubd.jpg

Im still a bit new at blender and would like some advice on how to prevent triangles like this:

http://img40.imageshack.us/img40/952/subdw.jpg

Thanks in advance =),

Kam

1111111111

thank you! =D seems so simple now =P but yes, thank you for the timely response <3

Sorry for a double post, but i have run into annother problem… i dont know what is causing this, but the hood is done, and when i put “set smooth” on theres weird dark spots in some places…

http://img193.imageshack.us/img193/8444/subdq.jpg

any idea how to fix this?

Thx,
Kam

In edit mode, select all your faces and flip your normals. ( CTRL+N )