Adding Custom Button on the Entity Entry part in MS CRM 4.0

Add the following code in the page load Event of Entity.

crmForm.all.sampleattribute.innerHTML = ''<button class='ms-crm-Button' onclick='ButtonClick();'>custom Button</button>'';

crmForm.all.sampleattribute_c.style.display = 'none';

ButtonClick= function() {

alert('alert from custom button click');

}