Help with using a field value to construct a URL parameter


I am new to Drupal and want to build a function to track package status. Since some moduels are still not available, I plan to use Drupal 7 instead of 8.

The business case is : The package is received in US and assigned a US tracking number (UTN). The package is then shipped to China. As long as it pass the Chinese customs, a Chinese Tracking number (CTN) is assigned to the package, and this CTN is used to retrieve shipping status in China.

I create a content type called ‘Package Status’. If has following fields:
Recipient Name
Recipient phone
Update date
Status message

I will post 5 nodes in sequential order for a given UTN package with following 5 different status messages, at 5 different update states:
(1) enter warehouse
(2) leave warehouse
(3) Flying to China
(4) In process in Chinese Customs
(5)Passed Chinese customs, a CTN is assigned

I will use a view to list all 5 nodes of a specific CTN, ordered by update date in ascending order. In this way, the package status is displayed in sequential order. A custom can search the status of his package by searching with the UTN.

The CTN is not assigned with its field being empty until step (5). I hope the view does following:

If CTN is not empty THEN
      Display something like following 
      <a href="******" target="_blank">Click to track status in China</a>
End If
Here ****** is the value in the CTN field

In other words, the link will not be displayed for the nodes of steps (1) ~ (4) since the CTN field is empty. At step (5) the CTN is not empty, then the views can extract the CTN value to create the clicking link.

My questions are:
(1) How to extract the CTN value and check whether it is empty in setting up a view?
(2) If not empty, how to attach the link with the node whose CTN is not empty ?

Any suggestion is sincerely appreciated!


Drupal version: