【加试题】小强用VB编写正整数十进制转换为十六进制的程序，运行界面如图所示。程序功能如下：在文本框Text1中输入待转换的十进制值，单击“十进制转换十六进制”按钮Command1，在文本框Text2中输出转换结果。

请在程序的划线处填写合适的代码。

Private Sub Command1_Click()

        Dim a As String,s As String

        Dim r As Integer,x As Integer

        x = Val(Text1.Text)

        s = ""

        Do While x > 0

  ▲                ‘①

            x = x \ 16

            If r > 9 Then

                a = Chr(r + 55)

            Else

                a = Str(r)

            End If

             ▲                ‘②

Loop                     

        Text2.Text = s

        End Sub