I am trying to find the last value in a column, then convert that value
(stored as "General") to seconds in the new sheet.

I've been trying:

=--(TEXT((LOOKUP(99^99,'[HBS wed.
USER.xls]Sheet1'!$F:$F)),"00\:00\:00")*86400)

but get a #N/A error.

Any help?
TIA
Greg