Lookup fields may not be used as the reference field on the right aside of a relationship if you need to have summary fields on the relationship. You might "trick" it from time to time to get it to not error on you, but the results will often be flaky - ie the Summary fields will not be correct.
1. Is there a way to make the link based on fields which are not lookup fields- for example [Related Location] and [Related Customer], ie those fields would typically not be lookup fields.
2. Alternatively it would not take much to make a formula URL button to update a data entry text field to match a formula field, then base your relationship on a clean data entry field that will work. However, you would need to click the button each day to update the links. Perhaps ACTIONS could also be used to maintain the integrity match between the formula field and the data entry field.
