Visual Studio Visual Basic -Sql Update Statment

Trying to update some fields to a sql database 2005 in sub FormClosing of datatype numeric(10, 2)
with the code below:

Try
            objConn.Open()
            With colCmd
                .CommandType = CommandType.Text
                .CommandText = "Update Settlement Set PreviouAdvDepositstxt = '" & PreviouAdvDepositstxtTextBox.Text & "', TransferGuestLedgertxt = '" & TransferGuestLedgertxt.Text & "', ActivityAdvdeposittxt = '" & Activityadvdeposittxt.Text & "'Where Sitetxt = 2 and PrimaryKey = (Select Max(PrimaryKey) from Settlement where SiteTxt=2)"
                .Connection = objConn
                .ExecuteNonQuery()
            End With
            objConn.Close()
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try

Im getting a error message of: Error converting data type varchar to numeric.
It happens when the number is more then 4 spaces past the Decimal because the number has a comma in it for example 1,000.00- I need the comma to display, but also need to import it into the sql database.

Any ideas