Anne, something like this works, I do not know if there are some drawbacks though...
_screen.AddObject('MyTimer1', 'MyTimer')
define class MyTimer as Timer
interval = 5000
enabled = .t.
function timer
this.Enabled = .F.
wait window 'Timer Fired' timeout 1
this.Enabled = .T.
endfunc
enddefine
"The five senses obstruct or deform the apprehension of reality."
Jorge L. Borges?
"Premature optimization is the root of all evil in programming."
Donald Knuth, repeating C. A. R. Hoare
"To die for a religion is easier than to live it absolutely"
Jorge L. Borges