How to handle the InputBox cancel button?

I type in the start date and the end date and execute a code of export from Outlook.

Sub ExportFromOutlook()
Dim dteStart As Date
Dim dteEnd As Date

dteStart = InputBox("What is the start date?", "Export Outlook Calendar")
dteEnd = InputBox("What is the end date?", "Export Outlook Calendar")
Call GetCalData(dteStart, dteEnd)
End Sub

I want when I press the "Cancel button" on any of the Inputboxes to exit the sub, not to get an error in the VBA code to debug it.