How can I declare a object that value change every time.

It's possible you may need to select different property/value pairs to identify the object. 

Also.... I'm not sure you have the correct syntax for FindChild.  The first parameter should be the property name (ObjectType, Caption, etc) the second parameter should be property value.  It looks like you have two values instead.  Please review the syntax of the FindChild at 

https://support.smartbear.com/testcomplete/docs/reference/test-objects/members/common-for-all/findchild-method.html