To avoid getting an error when passing a variable to a form, using If Not against the EOF (I believe means End of File) property.
If Not Me.Recordset.EOF And Not Me.Recordset.EOF Then
Dim stDocName As String
Dim stLinkCriteria As String
stDocName = "someform"
stLinkCriteria = "[recordnumber]=" & Me.[recordnumber]
DoCmd.OpenForm stDocName, , , stLinkCriteria
Else
MsgBox "No Record Selected!"
End If