OleDBException 0x80040e10 No value Given - vb.net

Question

The first part of this works correctly, when the Textbox value is null. It throws an exception however, when i try to filter search using the second part of the if statement.
The reason the table var is set that way is because the user has the option to load different tables.
The textbox string is the search parameter.
Public Class form1
Dim con As OleDbConnection = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source= .\Service.accdb ;")
Dim da As New OleDbDataAdapter
Private Sub getdata()
Me.Refresh()
Dim dt As New DataTable
Dim cmd As New OleDbCommand
Dim table As String = ComboBox1.Text.ToString
Dim txt As String = TextBox1.Text.ToString
If TextBox1.Text = Nothing Then
con.Open()
da.SelectCommand = New OleDbCommand("select * from [" & table & "] ;", con)
con.Close()
Else
con.Open()
da.SelectCommand = New OleDbCommand("select * from [" & table & "] where (External like '%" & txt & "%' or Internal like '%" & txt & "%' or Code like '%" & txt & "%');", con)
con.Close()
End If
Try
da.Fill(dt)
Catch ex As Exception
MsgBox(ex.ToString)
End Try
DataGridView1.DataSource = dt
End Sub
End Class
Any help would be appreciated.
EDIT
It seems that this bit of code is stopping it from searching correctly, however without it i cannot save to the DB..
Dim builder As OleDbCommandBuilder = New OleDbCommandBuilder(da)
builder.QuotePrefix = "["
builder.QuoteSuffix = "]"
So i am assuming i am missing a paramter from this section?