Not sure if this is what you want, but here is one approach:
Connect to customer sheet.
Left join orders to customers on [Customer ID]
Make sure [Customer ID] and [Order ID} are dimensions; if not, drag them to the Dimension list.
Duplicate the [Order value] field Drag the copy to the Dimension list.
Drag the copy to the Row shelf then right click and change its aggregation MAX([Order value (copy)])
Drag [Customer ID] to the Level of Detail shelf
Change the MAX([Order value (copy)]) to a dimension
You should have a discrete list of maximum order values, one for each [Customer ID].
Is this what you had in mind?
Michael W Cristiani