Option Explicit

Sub AddStylesFromList()
Dim MyStyle As Style
Dim bExists As Boolean
Dim i As Integer
Dim vStyle(19) As Variant
    vStyle(0) = "Stylename1"
    vStyle(1) = "Stylename2"
    vStyle(2) = "Stylename3"
    vStyle(3) = "Stylename4"
    vStyle(4) = "Stylename5"
    vStyle(5) = "Stylename6"
    vStyle(6) = "Stylename7"
    vStyle(7) = "Stylename8"
    vStyle(8) = "Stylename9"
    vStyle(9) = "Stylename10"
    vStyle(10) = "Stylename11"
    vStyle(11) = "Stylename12"
    vStyle(12) = "Stylename13"
    vStyle(13) = "Stylename14"
    vStyle(14) = "Stylename15"
    vStyle(15) = "Stylename16"
    vStyle(16) = "Stylename17"
    vStyle(17) = "Stylename18"
    vStyle(18) = "Stylename19"
    vStyle(19) = "Stylename20"

    On Error Resume Next
    For i = 0 To 19
        bExists = style_exists(ActiveDocument, CStr(vStyle(i)))
        If bExists = False Then Application.ActiveDocument.Styles.Add CStr(vStyle(i)), wdStyleTypeParagraph
        DoEvents
    Next i
End Sub

Function style_exists(test_document As Word.Document, style_name As String) As Boolean
    style_exists = False
    On Error Resume Next
    style_exists = test_document.Styles(style_name).NameLocal = style_name
End Function