Public Function IsLeapYear(lyear As Integer) As Boolean

If ((lyear Mod 4) = 0) Then
If (lyear Mod 100) > 0 Or (lyear Mod 400) = 0 Then
IsLeapYear = True
Else
IsLeapYear = False
End If
Else
IsLeapYear = False
End If

End Function

Option Explicit

Private Sub Command1_Click()
Dim y As Integer, ret As String

y = Val(Text1.Text)

If IsLeapYear(y) = True Then
ret = y & " 年はうるう年です。"
Else
ret = y & " 年はうるう年ではありません。"
End If

Label2.Caption = ret

End Sub

Private Sub Form_Load()
Text1.Text = Year(Now)
End Sub