Backend Database

I have put my data tables into another access database which resides on a
server.
After splitting the database. When I use seek, it tells me that it is an
invalid function.
I have linked the tables in the backend database to the current database.
my code is as follows :

Dim dbs1 As dao.Database
Dim rst1 As Recordset

Set dbs1 = CurrentDb
Set rst1 = dbs1.OpenRecordset("Customer Forecast")

rst1.Index = "Key"
rst1.Seek "=", estkey

before splitting the database, it worked fine. Why would this stop working.
The table in the backend database is indexed on "Key"

Thank you,
Gerry