Calling Functions Within A Script?

So far, I am creating a modeling program, similar to blender in which you can create 3D models.

The only problem ive had is exporting in game. I have a .obj exporter script, yet it is a editor script so it is apparently not usable in game!

The ISSUE I NEED YOU TO FIX IS..Calling this function in the script! -

My Code Of Thingy That I Need To Access :

 using UnityEngine;
 using System.Collections;
 using System.IO;
 using System.Text;
  
 public class ObjExporter : MonoBehaviour {
 
 public ObjExporter script;
 public GameObject ToBeExported;
  
     public static string MeshToString(MeshFilter mf) {
         Mesh m = mf.mesh;
         Material[] mats = mf.renderer.sharedMaterials;
  
         StringBuilder sb = new StringBuilder();
  
         sb.Append("g ").Append(mf.name).Append("\n");
         foreach(Vector3 v in m.vertices) {
             sb.Append(string.Format("v {0} {1} {2}\n",v.x,v.y,v.z));
         }
         sb.Append("\n");
         foreach(Vector3 v in m.normals) {
             sb.Append(string.Format("vn {0} {1} {2}\n",v.x,v.y,v.z));
         }
         sb.Append("\n");
         foreach(Vector3 v in m.uv) {
             sb.Append(string.Format("vt {0} {1}\n",v.x,v.y));
         }
         for (int material=0; material < m.subMeshCount; material ++) {
             sb.Append("\n");
             sb.Append("usemtl ").Append(mats[material].name).Append("\n");
             sb.Append("usemap ").Append(mats[material].name).Append("\n");
  
             int[] triangles = m.GetTriangles(material);
             for (int i=0;i<triangles.Length;i+=3) {
                 sb.Append(string.Format("f {0}/{0}/{0} {1}/{1}/{1} {2}/{2}/{2}\n", 
                     triangles[i]+1, triangles[i+1]+1, triangles[i+2]+1));
             }
         }
         return sb.ToString();
     }
     
     void OnGUI () {
     if(GUI.Button(new Rect(60,290,25,200),"Export Creation As .Obj"))
         
     }
  
     public static void MeshToFile(MeshFilter mf, string filename) {
         using (StreamWriter sw = new StreamWriter(filename)) 
         {
             sw.Write(MeshToString(mf));
         }
     }
 }

Basically, I need to call this function at the bottom of the script from a C#, (I could also do it from a JAVA script if thats the only thing you can help with!)

CALL THIS FUNCTION...

  public static void MeshToFile () {