Prevent userform from transfering data if duplicate value

[Weasley0307]

Hi. I have a userform for transfering the data into sheet1. But I want to make sure the userform does not save the data if the OC/SC No. textbox's value is duplicated with the existing data in column C of the sheets. As shown in picture below. I want to have a pop up msgbox saying that there is duplicated value with column C and it does not transfer the data, which means it will exit the private save data sub that i have.

 

[DanteAmor]

Add the following code to your "Save" button.

Change TextBox4 to the name of your textbox OC/SC No.

Private Sub CommandButton1_Click()
  Dim f As Range
  
  With TextBox4
    If .Value = "" Then
      MsgBox "Enter OC/SC No. "
      .SetFocus
      Exit Sub
    End If
    Set f = Range("C:C").Find(.Value, , xlValues, xlWhole, , , False)
    If Not f Is Nothing Then
      MsgBox "there is duplicated value with column C and it does not transfer the data"
      .SetFocus
      Exit Sub
    End If
  End With
 
  '
  '
  'Here continues your code to pass the data to the sheet.
 
 
End Sub

Note:
If you have questions about how to adapt the code, it would be a good idea to put all your code and the names of each control here.
You should put this in the original post, this would help provide you with a better answer.