二個字串一次各取一個合併： 一個由左而右，一個由右而左

Public Class Form1
    Dim i, str1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim s1 = "1234567890"
        Dim s2 = "ABCDEFGHIJ"
        For i = 1 To 10
            str1 = str1 & Mid(s1, i, 1) & Mid(s2, 10 + 1 - i, 1)
        Next
        MsgBox(str1)
    End Sub
End Class