Access Form's Statusbar Panel From Library File

I have a windows forms app with a statusbar. In the form's code, I use
a delegates and spawn a worker thread to get processing off of the GUI
thread. Then in the worker thread I access a function in a library
file. The function needs to be able to update some of the forms status
bar panels. I have had great success in doing the following...

Invoke(new UpdateStatusDelegate(this.UpdateStatus), new object[] { "My
Message" });

BUT, it doesn't work from the function in the library file. I have
gotten it down to two error messages on compile:

1. The name 'Invoke' does not exist in the current context
2. An object reference is required for the nonstatic field, method, or
property 'MyNamespace._MyFormInstance.UpdateStatus(string)'

First, I do not understand why the first error message is occurring. I
have all "using" statements in the library file set to the same as in
the form's code file. I am missing something, somewhere.

Second, I can see why the second message is occurring. The calling form
instance is non-static. But this doesn't cause any problem when using
the code snippet in the form's code file.

Any suggestions?