access form control open on event

Here is what I'm hoping to accomplish in Microsoft Access 2013:

1) Create a form (Form "x") with a series of checkboxes (Checkbox "xA", "xB", "xC")

2) Create an event procedure so that upon selecting checkbox "xA", a new form/window will launch (form "x1") with additional controls (checkboxes, buttons, etc...) while keeping form "x" open. Similarly for checkboxes "xB" and "xC".

I've tried doing the following in VBA to no avail:

Private Sub xA_Click()

Me.xA.DefaultValue = False

If Me.xA = True Then

DoCmd.OpenForm (x1)

End If

End Sub

Sorry if the format above is incorrect. This is my first time and I'm having trouble with the code builder.