I created 5 custom pages.

While setup is in progress, I want to change the x, y coordinates or size of a specific control.

I tried the following but to no avail:

For example, change the y coordinate of the 1037 ID control from 15 to 20.

GetDlgItem $R0 $HWNDPARENT 1037
System::Call 'user32::MoveWindow(i$R0,i15,i20,i 280,i 18,i0)' 

The above method is the correct method.

However, there was a mistake in my controlID value 1037 -> 1035…
(Assumes : Windows 7 or higher., NSIS3.x)

Thanks to Remy, I was able to quickly figure out with Spy++ that I had written the control ID wrong

(because the handle address was different).