[1.7.10] [Solved] How do you use part of a texture for a GUI

[Silly511]

I am making a GUI for a energy storage block I made, and I want a bar indicating how much energy is stored in the storage block. I know you can have more than one texture in the same file, but how do I implant the texture? I am using

drawTexturedModalRect

for my main texture but how do I select a part of the image?

[Silly511]

I can't figure out what coords to use there. Could you give me a image of which set of coords correspond to which places on the gui texture?

 

EDIT: Never mind, I figured it out. I was thinking about it to hard.