NGUI - move label in absolute pixels

I'm creating an item tooltip for my game using NGUI - consisting of a sprite background and multiple UILabels.

I'm moving these UILabels down/up depending on the number of rows of the previous ones - for instance, if an item has a longer description, the label showing its stats will be moved lower down to not overlap. I'm using this simple code to move the labels - labelText4 is an UILabel:

 labelText4.transform.position = new Vector3
 (
 labelText4.transform.position.x, labelText4.transform.position.y-0.055f,
 labelText4.transform.position.z
 );

This code for instance moves the fourth label down a bit.

However, this does not move the label in absolute pixel values - in other words, if I change the screen resolution it will not be moved correctly. How can I move an UILabel through script like I move any NGUI element in the Unity Editor?