It's not clear from your descripton what you want and what the problem is.
Maybe making your form Frm1 a Top-Level (ShowWindow=2) will work for you?

>
>I have a large form (let's call it Frm1) which covers almost fullscreen.
>Its layout propeties are:
>AlwaysOntop = .F.
>Desktop = .T.
>MDIForm = .F.
>ShowWindow = 0
>WindowState = 0
>
>I have buttons on Frm1 which bring up VFP's table designer and View designer
>The problem is those VFP designer always get blocked by this large form Frm1...
>Is there any way I can control layout properties of those VFP designer?
>
>In fact what I want is, if Frm1 is brought up, it must NOT be blocked by other windows except for those windows brought up by Frm1 itself... how would I achieve this?