How do I get Texture from material

I have 14 buttons with different textures. I made a sprite sheet and assigned to the texture of a Material. I am trying to use the SetTextureOffset() to get the required image from the sprite. I am sure that my offset and tiling are correct (because I can see them in the preview windows of the material). When I try to display it on my device, I just get a black rectangle. I am using UnityPro iOS. and the app is for iPAD only.

How can I get the desired Texture from Material? Also, I am not sure if “_MainTex” is the right parameter?

Here is my code:

Material agentMaterial = Resources.Load("AgentMaterial") as Material;
agentMaterial.SetTextureOffset("_MainTex",new Vector2(0.0f,0.875f));
Texture tex = agentMaterial.GetTexture("_MainTex");
GUI.DrawTexture (scaleRect(500,20,250,250),tex);

I am pretty sure GetTexture returns the full texture, I dont believe you can use material like what you are doing…try looking at this