State tax filing

I live in Washington State and primarily telecommute from Washington for my job in Oregon. On occasion, I will work a full day in Oregon. I already understand that I can prorate my tax filings for the days I work in Washington versus the days I work in Oregon. However, more often then not, I will start my day working from my home office in Washington, will drive to my business office in Oregon for a one to two hour meeting, and then drive back home where I will work the remainder of the day. Does this count as a Washington workday or an Oregon workday? I am currently tracking the hours I work part days in Washington versus Oregon.