[Gambas-user] creating objects from code into a tabstrip

[M0E Lnx]

In a form, I have a tabstrip.
The tabstrip's .count property is not defined until some conditions are met

After the tabstrip's .count property has been set, I want to fill each
tab of the tabstrip with a button, textlabel, textbox etc

When i create my objects, how do I tell it which tab to go to?
Seems that the only tabstrip itself enherits the container property,
but the tabs in it do not.
I have already tried something like this

bt = new button(tabstrip1[1]) as "button"

but that says bad use of virtual class

Please help