(posting here in case it helps others - )
... I will say I've got it solved. it's not elegant but I'll detail it here in hopes it helps another.
First - BITools or BITs is awesome and I love this little item! I use Hubitat as the center of my smart home. This product has an add on (community written) that connects to OpenWeatherMap. This service provides tons of things including images, forecast data, and a myriad of parameters, including UV and Luminescence (I'm going to call lumens for now). Bits, which does have UV, pulls it's data from Wunderground.com and the UV value is no longer being provided. Add that to Wunderground not having a luminescence value is what started me on this path.
I use the lumens value in my smart home to determine if a light should go on in a room when someone enters. I also want to use it as a Trigger in BlueIris to have the camera change from Day/Night in a controlled way. The Automatic Day/Night I have on my security cameras is mediocre at best.
So I wanted to use BITs to display the Lumens and UV values so I could monitor and fine tune my cameras. Okay. so thats the background.
HUbitat is a web based device. It has NO file management. but recently it has begun allowing storing of files in a Local folder. This is a recent thing and still in Beta. So - I write a 'rule' in hubitat, that it takes the values of UV and Lumens from OpenWeatherMap and saves them to a variable, then writes those 2 variables into a txt file and stores that file in the Local folder. I have this 'rule' run every 15 minutes, and overwrite the existing file with the latest values.
I then installed in my CamServer where BI runs (a Windows 2012 machine) a VERY old tool called Wget - a sort of 'walker' or 'spider' as we used to call it, and call that local file but in Html format. ie; '192.168.x.x/local/uv_lumens.txt' and then write THAT output into a txt file in the bits folder. I also force the wget to do an overwrite of the file... This works perfectly!
FInally, I simply added a scheduled task in Windows to run a batch file of this Wget line and scheduled it for every 10 minutes. It would be hard to set schedules on both the hubitat and scheduled tasks so they fired in proper order, so I opted for this 'cheat' method.
I then went into Bits, updated one of the macro values to point at my newly created file and placed in the camera overlay and ... viola. success!