Sort 3 textboxes to get an order for a specific formula

Hi,
I'm fairly new to VBA programming and I stumbled upon a problem concerning sorting my data from textboxes from small to big and use them in a formula to calculate the girth of a box. (Girth formula is [(adding 2 smallest dimension)*2+largest dimension])

The problem is, I keep having an error sorting my data before i can even use this formula. What I have now is:

 Dim W As Variant
    Dim D As Variant
    Dim H As Variant
    Dim Small1 As Variant
    Dim Small2 As Variant
    Dim Small3 As Variant

W = TextBox41.Value
D = TextBox40.Value
H = TextBox39.Value

 Small1.Value = Application.Small("W,D,H", 1)
 Small2.Value = Application.Small("W,D,H", 2)
 Small3.Value = Application.Small("W,D,H", 3)
TextBox58.Value = ((Small1.Value + Small2.Value) * 2) + Small3.Value

Thanks for helping. I've already been searching for this for about a week at the moment (and about 1 day on this forum).