Private Sub cmdMultyply_Click()
Dim cell_value As Double
Dim rng As Range
Dim cell As Range
Dim nmr As Variant
Dim formula As String

nmr = Application.InputBox("Insert a number.", "INPUT", Type:=1)

If nmr = False Then Exit Sub

Set rng = Selection

For Each cell In rng
    If cell.Value <> "" Then
        cell_value = cell.Value
        formula = Replace(cell.FormulaLocal, "=", "")
        cell.FormulaLocal = "=(" & formula & ")" & "*" & nmr
    End If
Next

Unload Me
End Sub