help about code VB6

I downloaded a source code VB6 about pharmacy program and its work but i always got this error

Run-time error 3709
The connection cannot be used to perform this operation. It is either closed or invalid in this contextand after i click on Debug i found this code

Code:

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rs.Open "Select Billno from Orders", cn, adOpenKeyset, adLockOptimistic

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and this is the complete code

Code:

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Private Sub NewMode()
rs.Open "Select Billno from Orders", cn, adOpenKeyset, adLockOptimistic

If rs.EOF Or rs.BOF Then
Me.Text1(0).Text = 1
Else
rs.MoveLast
Text1(0).Text = rs.Fields(0) + 1
End If

Text1(1) = Date
Text1(2) = ""
Text1(3) = 0
Text1(4) = 0
Text1(5) = 0
iGrid1.Clear True
Set rs = Nothing
End Sub

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The source code which i downloaded in this website
http://www.planet-source-code.com/vb...68020&lngWId=1

welcome to the forum,
in that website there are lots of things, but u told simply this is the complete code????

Have you modified the Data Link to reflect the location of your Database? As distributed it expects the Database to be at: 'D:\VB PROJECTS\Pharmacy\Pharmacy.mdb'. The (many) 'On Error Resume Next' statement(s) is / are stopping you from seeing problems.

Have a read of the Database Development FAQ which, contains the answers you may need as well as useful examples too.