how can we pass an object defined in one unit to another

Hi,

You need to return required value from the function like it was advised by Vinicius.

Like this:

//OpenFB unit

function openurl()
{
  var browser;
  var page;

  Browsers.Item(btChrome).Run("https://www.facebook.com/");
  browser = Sys.browser();
  page = browser.Page("*facebook.com*");
 // page.NativeWebObject.Find("name","websubmit","BUTTON").Click();  this code is working when executing from unit OpenFB

  return page; // <== added line
}

//Unit B

//USEUNIT OpenFB
function mandatory_check()
{

    var page;

    page = openurl();   // <== OpenFB. is not required because of //USEUNIT OpenFB directive
    page.NativeWebObject.Find("name", "websubmit", "BUTTON").Click();
 }