Using a macro, how can I write the value from
Workbooks("Wb1").Range("Rng1") to Workbooks("Wb2").Range("Rng2") when
"Wb2" is closed?

Conversely, how can I read the value from
Workbooks("Wb2").Range("Rng2") into Workbooks("Wb1").Range("Rng1") when
"Wb2" is still closed?

I don't want to use links because I need complete control over the
event and I need to pass data in both directions.