You can automate the process of taking back up of VM on azure by use of Powershell. The following command can be used to perform this operation -
Start-CopyAzureStorageBlob -SrcContainer vhds -SrcBlob $blobName -DestContainer vhds -DestBlob $blobName -Context $sourceContext -DestContext $destContext -Force
The whole process is mentioned at the link - [http://blogs.msdn.com/b/microsoft_press/archive/2014/01/29/from-the-mvps-copying-a-virtual-machine-from-one-windows-azure-subscription-to-another-with-powershell.aspx?Redirected=true][1]