create a texture from a spritesheet cocos2d

Question

Hey all Basically all i want is to create CCTexture2D objects from a spritesheet. I can make individual sprites from

charSpriteCur = [CCSprite spriteWithTexture:charSheet.texture rect:CGRectMake(136, 0, 136, 223)];

but i want to get individual textures from a spritesheet so that i can use

[mySprite setTexture:tex]; to change the sprite as required. I dont need it to be an animated sprite i just want to be able to change its texture when i want using a spritesheet. any ideas with this or what is the best approach? thanks g