请根据算法将下列程序补充完整。

Function prime（a As Integer） As Boolean

    Dim j As Integer

    prime = True

    j = 2

    Do While prime And j <= a \ 2

       If a Mod j = 0 Then

           prime = False

         Exit Do

       End If

             ____

         Loop

End Function

Private Sub Command1_Click（ ）

Dim i As Integer, a As Integer, b As Integer

Dim count As Integer

a = Val（Text1.Text）

b = Val（Text2.Text）

        For i = a To b

           If ____ = True Then

               List1.AddItem Str（i）

               count = count + 1

           End If

Next i

Label1.Caption = "素数共有" + Str（count） + "个!"

End Sub