"append a live table". I believe what you mean is "to append records to a table in use by someone [else]". Assuming that ...
Assume that your tables have a single-field primary key called, for our purposes, "PK"
var
tcMyNewData tCursor
tcLiveTable tCursor
endVar
tcMyNewData.open(":Alias:MyNewData"

tcLiveTable.open(":Alias:LiveTable"

tcLiveTable.edit()
scan tcMyNewData :
tcLiveTable.setRange("PK", "PK"

if tcLiveTable.nRecords() < 1 then ;all-new record
tcLiveTable.insertRecord()
tcLiveTable.copyRecord(tcMyNewData)
tcLiveTable.postRecord()
else ;updating existing record
if tcLiveTable.recordStatus("Locked"

= False then
tcLiveTable.copyRecord(tcMyNewData)
tcLiveTable.postRecord()
else ;someone is editing it !
;note that this record wasn't copied,
;and come back later to do it !
endif
endif
tcLiveTable.setRange()
endScan
should allow you to update another table safely, even if someone else is editing it. If you know that they'll only be viewing it, you can cut out the part about locking and just copy the new data over the old record.
hth
Mike