How Can I Valid A Compound Key With Dlookup Function

[CMontoro]

In a form named PRODUCTION there are 3 text box for invoice data: xtype, xserie, xnumber

I need valid this data from the INVOICE table, where its key is a compound key (TPINV+SERINV+NUMINV)
I tried with

Private Sub xnumber_AfterUpdate()
Dim searchinv as string
searchinv=Dlookup("*","[Invoice]", [tpinv]="& Forms![production].[xtype] and [xserie]= &Forms![production].[xnumber] and "&Forms![xnumber]
If searchinv ="" then
MsgBox ("Invoice doesn't exist'")
Cancel = True
End If
End Sub

... but it doesnt work
Please help me

Thanks in advance
CM

 

[pbaldy]

Your opening and closing of quotes around the form references is completely goofed up (and the formula looks incomplete at the end). Here's a reference you may find helpful, particularly the example of a multiple criteria lookup at the end.

http://www.mvps.org/access/general/gen0018.htm