I have a form with a series of dropdowns that are used by a lookup rule to fill a single line (our budget code). That budget code determines the routing the form will take for approvals. When there's an exception to our normal budget tables, an approver can type a new budget code into the single line. 

The problem arises with the subsequent approver. In Chrome (currently 63.0.3239.84), the form loads with the overridden budget code and all is well. In IE (currently 11.1770.14393.0), the lookup fires and replaces the budget code with the original one based on the dropdowns.

How can I control this behavior? If the code is manually entered, I need it to stay that way unless someone takes action to change it (e.g. actually changing the selections in the dropdowns).