Bạn thử dùng code này:
Private Sub TextBox1_Exit(ByVal Cancel As MSForms.ReturnBoolean)
With Worksheets("sheet1")
If TextBox1.Text <> "" And Not .Range("a:a").Find(TextBox1.Text, _
LookIn:=xlValues, lookat:=xlWhole, MatchCase:=False) Is Nothing Then
MsgBox "Ma hang: " & TextBox1.Text & " da ton tai. Vui long nhp lai ma moi " _
, vbExclamation, "Loi trung ma hang"
TextBox1.Text = Clear
Cancel = True
Else
Range("a65536").End(xlUp)(2).Select
Application.Selection.Value = TextBox1.Text
Cancel = False
End If
End With
End Sub
[COLOR=Green]' Chong ma trung hay long[/COLOR]
Private Sub TextBox1_Change()
TextBox1 = UCase(TextBox1)
With Application.WorksheetFunction
If .CountIf(Sheet1.Range("A2:A5000"), TextBox1) > 0 And TextBox1 <> "" Then
MsgBox "Khong nhap trung hay long ma"
TextBox1 = ""
End If
End With
End Sub
[COLOR=Green]'===========================================================
'Chong long trong ma da co[/COLOR]
Private Sub TextBox1_BeforeUpdate(ByVal Cancel As MSForms.ReturnBoolean)
With Application.WorksheetFunction
If .CountIf(Sheet1.Range("A2:A5000"), TextBox1 & "*") > 0 And TextBox1 <> "" Then
MsgBox "Khong nhap long ma"
TextBox1 = ""
Cancel = True
End If
End With
End Sub
