How do I solve this invalid property value? Error 380

[vbaNumpty]

I am trying to concatenate some values if a checkbox is activated in a userform, but it keeps giving me the 380 error. What am I doing wrong?

Private Sub NeedReview_Change()

    Dim existingNotes As Variant
    Dim needRev As Variant
    
    needRev = " - NEEDS REVIEW"
    existingNotes = CustomerBox.Value

    If NeedReview.Value = True Then
        CustomerBox.Value = existingNotes & needRev
    Else
        CustomerBox.Value = Left(CustomerBox.Value, Len(CustomerBox.Value) - 15)
    End If
        
End Sub

 

[Domenic]

Which line is causing the error?

Maybe this line CustomerBox.Value = Left(CustomerBox.Value, Len(CustomerBox.Value) - 15)?

Probably when CustomerBox contains less than 15 characters?

 

[vbaNumpty]

Which line is causing the error?

Maybe this line CustomerBox.Value = Left(CustomerBox.Value, Len(CustomerBox.Value) - 15)?

Probably when CustomerBox contains less than 15 characters?

No, its the following line:

CustomerBox.Value = existingNotes & needRev

There will never be an instance where the amount of characters is < 15. It's impossible

 

[Domenic]

Is the MatchRequired property of CustomerBox set to True? If so, the value would have to be a valid item from the combobox.

 

[vbaNumpty]

Is the MatchRequired property of CustomerBox set to True? If so, the value would have to be a valid item from the combobox.

That must be it. Thanks