Hi Paul,

Save the code below in PRG file. Create new project and add this file. Build executable from the project.

_SCREEN.Visible=.F.

LOCAL oParent
oParent = CreateObject('Tparent')
oParent.Visible = .T.
READ EVENTS
* end of main

DEFINE CLASS Tparent As Form
	Width=500
	Height=250
	ShowWindow=2
	Caption='Main form'
	Autocenter=.T.
	
	ADD OBJECT cmd As CommandButton WITH;
	Left=190, Top=200, Width=120, Height=27, Caption='Child form'

PROCEDURE cmd.Click
	LOCAL oChild
	oChild = CreateObject('Tchild')
	oChild.Show(1)

PROCEDURE Destroy
	CLEAR EVENTS
ENDDEFINE

DEFINE CLASS Tchild As Form
	Width=250
	Height=120
	ShowWindow=1
	Caption='Child form'
	Autocenter=.T.

	ADD OBJECT cmd As CommandButton WITH;
	Left=85, Top=80, Width=80, Height=27, Caption='Close'

PROCEDURE cmd.Click
	ThisForm.Release
ENDDEFINE

For demonstration purposes I used classes defined in PRG code. Better use Form designer. Create parent form and child forms. Call child forms not through CreateObject, use DO FORM instead.