Workflow Issue: How to record an inventory invoice before the inventory is received

We are having a workflow issue we need help with.  Our warehouses are in Alaska.  Our inventory vendors are in the lower 48 states and send inventory invoices weeks before we receive the inventory in Alaska.  For planning purposes, we want to get these invoices into our Acumatica system before the inventory arrives.  How can we achieve this goal?  What workflow can we adopt?  

Now we are reverting back to Excel spreadsheets and other pre-ERP solutions. Your help is greatly appreciated.