Displaying percentage on GUI

Hi everybody

I want to make an exp bar for my RPG, and I want to display the current exp as a percentage of the needed exp. So I've made this script:

 var maxexp = 50;
 
 var curexp = 10;
 
 var controlTexture : Texture2D;
 
 
 
 function Update () {
 
 
 
 if (curexp < 0) {
 
 curexp = 0;
 
 }
 
 
 
 if (maxexp < curexp){
 
 curexp = maxexp;
 
 }
 
 }
 
 
 
 function OnGUI () {
 
 
 
 if (maxexp >= 0){
 
 GUI.Button(Rect (0,78,500,26), maxexp.ToString(), "box");
 
 }
 
 
 
 if (curexp >= 0){
 
 GUI.Button(Rect (0,78,(curexp/maxexp*100),26), curexp/maxexp*100.ToString(), "box");
 
 }
 
 }

But when I add the script to a game object, it only displays the needed hp bar, and the bar displaying the percentage does only appear as a small bar at the left side of the screen, without displaying a number. And it also displays an error which says that the character T isn't expected.

Please help me