Try something like this:

In first form where you call the second form:

1. Create property: lWaitForSecondForm = .T.
2. In method to call second form:

...
thisform.lWaitForSecondForm= .T.
DO FORM MySecondTopLevelForm WITH thisform
DO WHILE thisform.lWaitForSecondForm
  =INKEY(1,'H')
ENDDO
....

In the second form:

1. Create a property to hold the object reference to first form: oFirstTopLevelForm = .NULL.
2. In Init method:

LPARAMETERS poFirstTopLevelForm
thisform.oFirstTopLevelForm = poFirstTopLevelForm
...

3. In Destroy method:

thisform.oFirstTopLevelForm.lWaitForSecondForm = .F.
...

This should cause the first to wait in the loop until the destroy event occurrs in the second form.