用do loop描述判断一个数是否为素数的算法。

Private Sub Form_Click()
Dim a As Integer
Dim b As Boolean
Dim n As Integer
a = InputBox("输入数字：")
n = 2
b = True
Do While n <= Sqr(a)
If (a Mod n = 0) Then
b = False
Exit Do
End If
n = n + 1
Loop
MsgBox a & IIf(b, "是", "不是") & "素数"
End Sub

Private Function sushu(ByVal n As Long) As Boolean
Dim i As Long
For i = 2 To n - 1 '从2到N-1
If (n Mod i) = 0 Then Exit For ’如何N与I 求余=0 则跳出循环
Next i
If i = n Then sushu = True
End Function

Private Sub Command1_Click()
Dim A As Long
A = Val(Text1.Text)
If sushu(A) = True Then
MsgBox A & " 是素数", vbOKOnly, "最恨VB的素数判断"
Else
MsgBox A & " 不是素数", vbOKOnly, "最恨VB的素数判断"
End If
End Sub