I have a form,frmDonationsMain, in which the RecordSource is tblCustomer.  
This form has only one field, CustomerID field.  CustomerID is the Pkey in 
tblCustomer.

The first subform is frmDonations and this has CustomerID and DonationID 
as the PKey Both forms are linked by CustomerID.

The next subform, frmDonationsDetails, had DonationsDetailsID as the Pkey 
and also have DonationsID which links these two forms.

I put an unbound cboBox named cboCus on the main form which displays 
Customers from tblCustomer.

The procedure below is attached to the afterupdate event to search and 
display  customers
So I can add donations

Dim rst As ADODB.Recordset, cnn As ADODB.Connection, strSQL As String
    Set cnn = CurrentProject.Connection
    Set rst = New ADODB.Recordset
    
    rst.Open "SELECT MemberID FROM tblCusromer;", cnn, adOpenKeyset
    rst.Find "CustomerID=" & cboCus    
    Me.Bookmark = rst.Bookmark

The problem I am having is that it takes a long time to find a customer.  
The first 3 or 4 customers are found  easily but after that I am getting 
the Hourglass for 25-30 seconds and longer.  In some cases I have to end 
task because it takes so long.

I remember seeing something saying  that if there are more than one 
subform the results are unpredictable.
Can someone comment on my case?