Pygtk cellrender combox + progress bar in a treeview

Question

So the issue is if the combobox of the row is open (pop'd up) and I update the progress bar value

self.store.set(iter, 2,  self.core.progress )

Then the combo box immediately closes, if the update happens a couple of times a second the combobox is useless...

Is there a way to update the progress bar without causing the combobox to close?