I will try to give a reliable estimate if I have enough information. If the task is very straight forward I can give a fixed price although I may have to include contingency for unknowable aspects.
On more complex jobs it’s not easy to give a fixed price unless I work with the detail. In these cases you would naturally be worried about open-ended cost. So sometimes the best way forward to satisfy the client and myself the Excel contract if I can spend an agreed time to scope the work and perhaps even work up a prototype or mock-up spreadsheet solution and report back with a reliable estimate before going ahead with the job.
When doing the job I will report back to you on hours spent regularly and professionally. Large jobs have a project plan stepped out which I will provide.
A brief initial consultation over Zoom or MS Teams or even over the phone is great way to explore your needs to get the ball rolling.