VBA User form gives warning if duplicate is found - vba

Question

I think I need to try and make this question easier. So here goes;
I am creating a User form in Excel that will act as a data capture form.
In this form I have a Textbox called PolBX In this a is placed and at submission data in PolBX is copied into the "G" column using this code
Cells(emptyRow, 7).Value = PolBX.Value. This works great.
I discovered that there may be instances where the User may accidently use the same Unique Id number twice. so I am trying to find out how to code it that after the User has entered the Unique Id number it would check for that string (Consists of letters and numbers). if it finds the string already in the 7th column(G) it must say something like
"Policy number already Used, please try again"
I am thinking I will need to use the following subroutine
Private Sub PolBX_AfterUpdate()
End Sub
Can some please assist with creating this code...
Also can you please explain what you are doing as I started VBA about a week ago

Answer 1

You can add the following code to search for your policy number, and if nothing found then PolLookup = Nothing.
Option Explicit
Sub Test()
On Error GoTo ErrHandler
Dim ws As Worksheet, PolLookup As Range, LookupRng As Range
Set ws = ThisWorkbook.Worksheets(1)
'This is the range you want to search, it can be a long range
'or it can be a single cell.
Set LookupRng = ws.Range("A:A")
'Range.Find is looking for your value in the range you specified above
Set PolLookup = LookupRng.Find("YourLookupValue")
'PolLookup = Nothing if it didn't find a match, so we want to use
'If <NOT> Nothing, because this suggests .Find found your value
If Not PolLookup Is Nothing Then
Err.Raise vbObjectError + 0 'Whatever error you want to throw for finding a match
End If
'Exit before you reach the ErrHandler
Exit Sub
ErrHandler:
If Err.Number = vbObjectError + 0 Then
'Handle your error. Do you want to stop completely? Or have the
'User enter a new value?
End If
End Sub
Basically, after your user enters their value in your UserForm, just make a call to this Sub to do a quick lookup.

Answer 2

Playing around I discovered a Much easier way! I included a Button with he following code attached
Private Sub CommandButton8_Click()
Search = PolBX.Text
Set FoundCell = Worksheets("sheet1").Columns(7).Find(Search,LookIn:=xlValues, lookat:=xlWhole)
If FoundCell Is Nothing Then
MsgBox "No duplicates found"
Else
MsgBox "This policy has already been Assessed" & "Please assess a different case"
PolBX.Value = ""
End If