DCount Function in VBA for two text fields and one numeric field (1 Viewer)

I have a form on input of data finds the duplicate feeding and warns. I used DCount function earlier with two text fields it was working perfectly. No I would like to add one more filed which numeric. How Do i go about it.

My fields are : Purchase_Order_Number = Text
Invoice_number = Text
Line_no = Number

you need to clarify your question, please provide some example data and show what you want from that example data

dcount("1", "theTable", "Purchase_Order_Number = " & chr(34) & [textString] & chr(34) & " and Invoice_number=" & chr(34) & [textInvoice] & chr(34) & " and Line_no=" & [txtLineno])