I'm not sure if what Xpression Prime version can or can't do but if it can't do visual logic, here is a script that does the same thing.
This will put the centre of the text box in the centre of the page. Change the + 540 to adjust the position.
Dim text as xpTextObject
dim height as integer
Self.GetObjectByName("Text1", text)
height = text.boundingbox.height
text.posY = height / 2 + 540
#XPression