How To Select Multiple Choice Field Options from a Report

This is possible if you set up a Relationship where 1 vendor has many Projects.  They will be typically connected by the field [Related Vendor] and the lookup field and "Proxy" will be Vendor name.

Then on the FORM properties on the Project record for the vendor field, you can specify the report to be used for the drop down list of vendors, and it can be a report filtered to just show Electricians.