Changing label text

I want to either change the text on a label, or free the label and make a new one. The problem is the label doesn't refresh until the window is resized.

Seems fine here. This example changes the label text on a 'timer' event:

Global title$="Label change example"
AppTitle title$

win = CreateWindow(title$,200,100,200,50,Desktop(),1)
lab=CreateLabel(":-)",15,5,200,28,win)

timer=CreateTimer(2)
Dim l$(3)
l$(1)="Hello" : l$(2)="Blitz" : l$(3)="User"
; --------------------------

Repeat
	event=WaitEvent()
	DebugLog "EVENT $"+Hex$(event)
	Select event
		Case $803 : Exit
		Case $103 : If EventData()=27 Exit
		Case $4001
		num=num+1 : If num=4 num=1
		SetGadgetText lab,l$(num)
	End Select
Forever

End

My fault, it works fine.