Moving a GameObject reffering to the coordinates of the parent Object

Greetings,

As the tile says, I would like to move a Gameobject reffering to the parent Gameobject. But when I try to do so via C# I can not change the position reffering to the parent Gameobject but to the "global" coordinates..Is there a way to change that?

For example, I try to use

for(int j = 0; j<5; j++){ button[j].transform.position = Vector3.Lerp(button[j].transform.position, new Vector3(button[j].transform.position.x, 1,4f, button[j].transform.position.z), t); }

The Gameobjects got 1,4 as y-coordinate within the parents coordination system, and I would like to use that. But it appears to be not that simple^^ I guess I have to change the point from where I get my coordinates in the code. An if I'm done with that, how would I change them back?

Thanks for any help.