主题：[求助]自定义函数计算月差

Dim d1 As Date = e.Form.Controls("DateTimePicker1").value
Dim d2 As Date = e.Form.Controls("DateTimePicker2").value
Dim m As Integer = (d2.year - d1.year) * 12 + (d2.month - d1.month)

怎么自定义函数