Get texture with UV Mesh Mapping

Hello all, I'm trying to get parts of a texture (I think this is called tileset), after reading some answers (mainly: how do uv work, how to best implement a tileset and breaking a big Texture2d into smallers) I get the following code:

 public Material mat;
 void Start()
 {
     Mesh mesh = new Mesh();
     
     float u = (float) 0.8; // up
     float d = (float) 0.6; // down
     float l = (float) 0.8; // left
     float r = (float) 1;   // right
         
     Vector3[] vertices = new Vector3[4];
     vertices[0] = new Vector3(l,u,0); vertices[1] = new Vector3(r,u,0);
     vertices[2] = new Vector3(l,d,0); vertices[3] = new Vector3(r,d,0);
     mesh.vertices = vertices;        
         
     int[] triangles = new int[6]{0,1,2,3,2,1};
     mesh.triangles = triangles;
         
     Vector2[] uvs = new Vector2[4];
     uvs[0] = new Vector2(l,u); uvs[1] = new Vector2(r,u);
     uvs[2] = new Vector2(l,d); uvs[3] = new Vector2(r,d);        
     mesh.uv = uvs;
     
     mesh.RecalculateNormals();
     
     GetComponent<MeshFilter>().mesh = mesh;
     GetComponent<MeshRenderer>().material = mat;
 }

Using it I can get only the image that I want on the mesh, but my questions is:

• How can I get this texture and use it in other places, like a GUI label or other material?

I hope my question is clear, thanks in advance and sorry my bad english.