Private Sub Vw_Click()
Dim x1 As Integer
Dim y1 As Integer
Dim z As Integer
r = 2
x1 = Val(x.Text)
y1 = Val(y.Text)
For x1 = r To y1 ' ERROR GRAVE GUARDSATE LA VARIABLE X.TEXT EN X1 Y ACA
             ' LA SOBRE ESCRIBIS CON R QUE ES 2 ...
             ' APARTE SI HACES QUE VAYA HASTA Y1 AL MULTIPLICAR POR R QUE ES 2
             ' VAS A LLEGAR HASTA Y1*2  
 
z = x1 * r
c.AddItem z
Next x1
End Sub

 
Option Explicit
 
Private Sub Form_Load()
Dim lng_i           As Variant
Dim lng_ret()       As Long
    For lng_i = 0 To GetParNumbers(-501, -11, lng_ret) - 1
        Debug.Print lng_ret(lng_i)
    Next lng_i
End Sub
 
Public Function GetParNumbers(ByVal ThisIniVal As Long, ByVal ThisEndVal As Long, ByRef ArrOut() As Long) As Long
Dim lng_i           As Long
Dim lng_d           As Long
    If ThisIniVal > ThisEndVal Then
        lng_i = ThisEndVal
        ThisEndVal = ThisIniVal
        ThisIniVal = lng_i
    End If
    If (ThisIniVal And 1) = 1 Then ThisIniVal = ThisIniVal + 1
    If (ThisEndVal And 1) = 1 Then ThisEndVal = ThisEndVal - 1
    lng_i = (ThisEndVal - ThisIniVal) \ 2
    If Not ((lng_i And &H80000000) = &H80000000) Then
        ReDim ArrOut(0 To lng_i)
        For lng_i = ThisIniVal To ThisEndVal Step 2
            ArrOut(lng_d) = lng_i
            lng_d = lng_d + 1
        Next lng_i
    End If
    GetParNumbers = lng_d
End Function