sSQL = "SELECT * FROM QuotationNew WHERE (((QuotationNew.[Quote No])= " & CLng(Me.Quote_No) & "))"
And if that fails try:
sSQL = "SELECT * FROM QuotationNew WHERE (((QuotationNew.[Quote No])= '" & CLng(Me.Quote_No) & "'))"
Make sure the data type you are supplying to the SQL statement matches the tables' field data type. Also, make sure that the Me.Quote_No combo box is actually supplying what you expect...test it.
If you don't get what you expect, then you may need to take a closer look at the properties for your combo box. You may find that you may need to use: Me.Quote_No.Column(x) in order to ooooz out the data you want