How can I make a GUI element move independently of the frame rate?

My Gui is a group which updates all the time from OnGui:

GUI.BeginGroup (new Rect (current_pos_x,current_pos_y, smartTabBackgroundImage.width, smartTabBackgroundImage.height));

When I move the group I have tried multiplying the current_pos_x by Time.deltaTime in the update loop but this doesnt seem to do anything.

EG…set the speed dep on FPS in the main Update() loop:

tabSpeed=Time.deltaTime*10;

& now move it…(This is called from OnGui())

while(current_pos_x<=tabShownPos_x)
	{
		current_pos_x+=tabSpeed;
		yield;
	}

Anyone any ideas?

Why not

if( current_pos_x<=tabShownPos_x )
    current_pos_x += 10 * Time.deltaTime;

inside the OnGUI(), and kill the need for that coroutine?