I found it.I put the controls in a panel and set autoscroll property of panel to true.When i display sip i set panel height equal to (form.height-sip.height).The problem is that i do not know how to scroll the panel to the control who has the focus before the sip appears.You should have a look at the Hardware library, there you can get SIP parameters.
You cannot resize a Form on the device, you must adjust the Controls.
Best regards.