nothing built in afaik but you can easily create your own.

questions is what exactly do you mean by loading?

there are a few things i can think of

1) creating the view object (mostly for deferred/dynamic views)
2) showing view on screen
3) changing data inside view

for what i am guessing you want you could for example use popup

Code:
Property pbIsLoading false

Procedure Popup
  Set pbIsLoading to true

  Forward Send Popup

  Set pbIsLoading to false
End_Procedure
this will fire every time a view is activated even if it is already active

if you only want it to work if the view was closed

Code:
Procedure Popup
  if (not(Active_State(Self))) Begin
    Set pbIsLoading to true
  End

  Forward Send Popup

  Set pbIsLoading to false
End_Procedure