Missing blitzplus function

I just bought blitzplus to do some fixes on some source code-
I usually use Blitz3D-

The source code I have been given contains a
SetWindowPos command that gives an function not found error-
This function also does not appear in the docs.

I have tried every combination of updating Blitzplus and the docs
from the website - still doesn't show up anywhere??

OK so searching around- this is not a Blitz command.... it's a microsoft
windows command

So the line using 'SetWindowPos' is trying to access a command from
windows- I'd love for somebody to explain in practical terms- what I
need to do to get this to work?

any help much appreciated

you will need to save a decls file in your userlibs folder to add win32 commands, here is an example someone posted in code archives