Hi,

The "Unable to get the VLookup property of the WorksheetFunction class" error means that your lookup value can't be found. If it's a number, you need to convert it, since the textbox contains text, not a true number. Perhaps this
Private Sub EntClientIDbx_AfterUpdate()
Dim lValue as Long
lValue = Clng(Me.EntClientIDbx.Value)
'Check to see if value exists
If WorksheetFunction.CountIf(Sheet1.Range("B:B"), lValue) = 0 Then
MsgBox "This is an incorrect ID"
Me.EntClientIDbx.Value = ""
Exit Sub
End If
'Lookup values based on first control
With Me
.ConfirmedClntName = Application.WorksheetFunction.VLookup(lValue , Sheet1.Range("Addressdata"), 3, 0) ------------Debug takes me here
.ConfirmedClntAddr1 = Application.WorksheetFunction.VLookup(lValue , Sheet1.Range("Addressdata"), 4, 0)
.ConfirmedClntCity = Application.WorksheetFunction.VLookup(lValue , Sheet1.Range("Addressdata"), 6, 0)
.ConfirmedClntPcode = Application.WorksheetFunction.VLookup(lValue , Sheet1.Range("Addressdata"), 7, 0)
End With
End Sub
As a side note, it would be more efficient to use Match to locate the position of the item rather than looking it up for every Vlookup call.