Loopix:
Code:

---

font font_Player = "arial",1,20;
string str_PlayerName = "Player";

text txt_PlayerNameIn
{
	pos_x = 0;
	pos_y = 0;
	layer = 15;
	font = font_Player;
	strings = 2;
	string = "Player Name: ",str_PlayerName;
}

function func_PlayerNameIn(PosX,PosY,SizeX,SizeY)
{
	txt_PlayerNameIn.Pos_x = PosX;
	txt_PlayerNameIn.Pos_y = PosY;
	
	SizeX += PosX;
	SizeY += PosY;
	
	txt_PlayerNameIn.visible = on;
	
	while(txt_PlayerNameIn.visible)
	{
		if(	mouse_left
			&& mouse_pos.x > PosX && mouse_pos.x < SizeX
			&& mouse_pos.y > PosY && mouse_pos.y < SizeY)
		{
			inkey(str_PlayerName);
		}
		
		wait(1);
	}
}

---

Just call the function "func_PlayerNameIn(PosX,PosY,SizeX,SizeY)" if you want to change the playername. PosX and PosY is the Position where the name gets displayed. You´ll have to click on the displayed text to change it so you have to say how big the text is with SizeX and SizeY.
If you want to make it invisible, just call txt_PlayerNameIn.visible = off; out of a function. The player name is stored in the string "str_PlayerName".

@aztec: I will try it when I´m done with my homework. It shouldn´t be very hard either