In Form1.cs, look for the comment at the start of the following code block. It should be pretty obvious where it starts and stops

Code:
					
                        // Try it as a SEQ map first
                        if (!loadmap(f + ".map")) {
                            // If it didn't work, try a LoY map
                            if (!loadmap(f + ".txt"))  {
                                bool foundmap = false;
                                for (int mapnum = 1; mapnum < 4; mapnum++)
                                {
                                    if (loadmap(string.Format("{0}_{1}.txt", f, mapnum)))
                                    {
                                        foundmap = true;
                                        break;
                                    }
                                }
                                //... Missing map       
                                if (!foundmap)
                                    MessageBox.Show("Couldn't find a map for the zone: " + f, "Error");
                            }
                            else
                                this.Text = BaseTitle + si.Name;
                        }
                        else
                            this.Text = BaseTitle + si.Name;
                        mapPane1.map.fillConColors();