Force SetFocus until input has been made

Hi guys,

I have this code that checks that my TextBox is not empty, and also formats it. But when one tabs through the field, a warning does pop up, but the cursor moves to the next field. How can I change/force the focus to that field until an input has been made?

i have tried SetFocus

Here is my code:

Private Sub txtStockSOS1_Exit(ByVal Cancel As MSForms.ReturnBoolean)

    If Not IsNumeric(txtStockSOS1.Value) And txtStockSOS1.Value <> vbNullString Then

        MsgBox "Sorry, only numbers allowed"
       
        txtStockSOS1.Value = vbNullString
        
        'Me.txtStockSOS1.SetFocus
        
    Else
txtStockSOS1.Value = Format(txtStockSOS1.Value, "#,##0.00")
    End If
    
End Sub

Thank you!