Please Help! Command Button not working!

[A. Smart]

I have a button on a form that when clicked opens a hyperlink that is
attached to a specific record. The code implies that:
If a record doesn't have a hyperlink display a message saying so!
If it does have a hyperlink open it.

I swear it used to work fine!!! Your help would be muchly appreciated! Heres
the code.

If (Nz(Me.Work_Instruction.Value, "") = "") Then
MsgBox "This Job has no Work Instruction.", vbInformation +
vbOKOnly, _
"No Work Instruction"
Else
Me.ViewWI.HyperlinkAddress = "\\AshleyS\Trim Line\" & _
Me.Work_Station & "\" & Me.Work_Instruction
End If

Exit Sub