How Split a 2nd row bar?

In MS Project you can plot up to 4 time bars for each task: in my case I have the 1st row bar linked to task start and finish and usual, and the 2nd row bar linked to start1 and finish1 fields. This can be done with the Format->Bar Style command.

Within the MS Project GUI I'm able to split both of the two bars, i.e. adding a blank gap between them, using the Split Command to split the Start1->Finish1 bar.
Now, I'm trying to replicate the same action using VBA, but the Split Method seems is able to split only the 1st row bar. Even browsing the Task Object methods and properties I cannot see any reference to the actual row used.

I also tried to record the splitting action with the macro recorder: if I split the 1st bar the Split Method is invoked, whereas if I split the 2nd row the resulting macro is empty.
Am I missing something or simply the current MS Proj VBA layer is unable to replicate all the GUI features? :banghead:

Thanks in advance.

Andrea