I didnt realise it was to be typed in during the command, I forget that you can have a command within a command.
Yes it works, odd though, the command normally asks for two curves to be picked and then enter radius.
This time it asked for a third tangent, pressing enter draws a circle through a point created after the first line is selected. To get round this I see one enters R instead of worrying about what third tangent it wants, then enter the radius value and you get a circle of your required radius.
In summary OnCrv in use with Tan Tan Rad circle tool asks for third tangent, so ignore and enter R and you get the command as one is used to.
I shall add that OnCrv to the list of essential tools now in my brain
Turning off layers to get at what I want, comes into the territory of my plea for select object indicates layers. I have many many layers, many colours, an extremeley complex build. If I was to select objects, view properties, find layer in layer palette, turn it off, repeat that 20 times or more , make notes of what was on and is now off, then turn them all back on again, the finding the layers stage of that would take half an hour, finding them again just as long. Nightmare.
Could I select the ones I dont want in perspective and use a command to lock them, then after running the command I do want, e.g. tan tan rad, select them and unlock them. Without going anywhere near having to find their layers ?
I do use perspective view to get at exactly what I need, there are times however that picking in that view, then reverting to an ortho view sees command fail. I found that to happen when projecting lines to a surface, it refused to work unless I started and ended in one window. It made choosing the stbd aircraft skin when the port one was nearest me very difficult ! Maybe it shouldnt do that but it did to me.