Disable Custom Button on Standard Page

Hi Prakhar,

This can be achieved by creating javascript button on the object and as per the condition specified, by using CSS to disable the button on Page Layout. Below is the code to achieve the same:-

{!REQUIRESCRIPT("/soap/ajax/25.0/connection.js")}
{!REQUIRESCRIPT("/soap/ajax/25.0/apex.js")}

if({!ISNUMBER(Employee__c.Salary__c)}){

this.disabled = false;
this.classname = 'btnDisabled';

}
else{

var btnService = document.getElementsByName("test");
btnService[0].value='Please wait...'; //Change the text
btnService[0].disabled=true;

}

Hope that helps for you.

Thanks.