// place a grid of guide lines over the active document
//var docRef = app.documents.add(500 ,600 ,72,"Test place guides" ,NewDocumentMode.RGB ); 

   var horizPosition = "Hrzn"; 
   var vertPosition = "Vrtc" ; 

   //Functions begin 
   function placeGuides( guideOrientation, guidePosition )
   { 
       var id2049 = charIDToTypeID( "Mk  " ); 
       var desc431 = new ActionDescriptor(); 
       var id2050 = charIDToTypeID( "Nw  " ); 
       var desc432 = new ActionDescriptor(); 
       var id2051 = charIDToTypeID( "Pstn" ); 
       var id2052 = charIDToTypeID( "#Pxl" ); 
       desc432.putUnitDouble( id2051, id2052,guidePosition ); 
       var id2053 = charIDToTypeID( "Ornt" ); 
       var id2054 = charIDToTypeID( "Ornt" ); 
       var id2055 = charIDToTypeID( guideOrientation ); 
       desc432.putEnumerated( id2053, id2054, id2055 ); 
       var id2056 = charIDToTypeID( "Gd  " ); 
       desc431.putObject( id2050, id2056, desc432 ); 
       executeAction( id2049, desc431, DialogModes.NO ); 
       return true; 
   }; 

var GuideSpacing = 100;
var Guide;
var i;
for ( i = GuideSpacing; i < app.activeDocument.height; i += GuideSpacing )
	Guide = placeGuides( horizPosition, i );
for ( i = GuideSpacing; i < app.activeDocument.width; i += GuideSpacing )
	Guide = placeGuides( vertPosition, i );