select all except locked object

Hi

i want to select all the object , but i locked certain object it show error

while submiting below code

myDoc = app.activeDocument;

myPageItems = myDoc.pageItems;

for (i=0;i<myPageItems.length;i++)

{

    myPageItems[i].selected = true;   

} 

can any one help me to modify above code to select all objects except locked object or i want to select objects outside active artboard

Thanks

Appu