Activating Stellarium from another application

Never done this, but sounds interesting. Are the arguments you are calling AppActivate with correct? (e.g. complete window title with version number?) I am of no further help, but see some discussion e.g. here:
http://www.mrexcel.com/forum/excel-questions/395115-appactivate-does-not-activate-application.html
You may even want to develop some data exchange:
http://qt-project.org/forums/viewthread/15980
G.

What exactly are you trying to do? Start Stellarium or bring a running instance of Stellarium to the foreground?

How exactly do you intend to exchange data between Stellarium and your VBA application?

To Georg: I tried all possible arguments you mention. The title I use reads "Stellarium 0.12.4". I'll investigate the links you provide. Thanks.

To Bogdan: my application contains the positions of DSO's, double stars and solar system object ephemerisses. The functionality focuses on steering my Meade LX200 (classic model) to these objects and logging all obervations with it, including my comments. Since my application no visualises objects, I looked for good - and free - astronomy program, and recently I found Stellarium as a very promising option.

After solving the AppActivate problem in the first place, what I want to do is steer Stellarium from my application with the VBA Sendkeys command. For objects with names it's easy, just "send" the F3 button to Stellarium and fill in the object name after
which I hope Stellarium will respond and show me the object.
Double stars in general have no names so I have to "send" a double star's position in RA and Decl to Stellarium. That seems difficult since I do not know Stellarium's key stroke to get to the 'Position' tab in the search window.

Thanks again in advance!

I recently added a hack to my 0.12.4 version of Stellarium which makes the StelScriptMgr create a little server that listens on a specific port. It receives lines of text on this port and, once the connection is closed, it then executes those received lines as a script.

It's really quite neat, because it allows the creation of external applications that can control Stellarium via its built-in scripting (and it's over TCP, so that app could be located on a different machine, or tablet, or phone, or whatever, if you set up access appropriately).

I was wondering if the devs might be interesting in adding a feature like this to Stellarium? Please...?
(I don't really feel confident that the way I've hacked it is particularly well done, since I'm coding with Qt for the first time, and hardly done any C++ before. Also I think it could do with someone who really understands how it should abort and clear up, or queue up for later execution, when it receives a new chunk of script before it's finished running the previous one, 'cos mine didn't quite work right under that situation...)

 It wasn't actually that hard to do, even for me (a couple of days of researching Qt, and trying to understand the existing code for scripting, and adding the server code), so I'm sure the devs could figure out how to get it in there within a few hours.
Any takers...?

You can create a branch with your code and propose this feature to merge with trunk.

What I do is the following:

Manually
I highlight the object designation (e,g, NGC 1040), usually in a spreadsheet, but can be in any doc.
Then Control/C to load the clipboard.
Then I switch to the Stellarium app running.
Then Control/F to popup the find window.
Then Control/V to load the clipboard contents into the find field.
Then Control/1 or Alt/1 to point my scope at the object.

I know, this sounds laborious, but it can be fully automated with Hotkey, with a simple script which emulates the above sequence.
Then it's:
highlight object designation.
Enter Hotkey.

Especially good in the dark!