Can anybody tell me how I can combine the geo objects of one relation to one single object? I reckon the Object Combine function is right one, but I have no idea how to specify the code...
Have a look at the MapBasic Reference guide. Pages 150-151 contain the syntax for the Objects Combine function. You might also find the Objects Combine statement useful. The syntax for that is found on pages 465-466.
You may also want to have a look at the Create Object statement which is on page 221. Specifically,
Create Object As Union.