[plt-scheme] Scheme: Subroutines

I am having trouble creating subroutines within scheme. I have cross referenced sub routines in help desk quite often, and come up with nothing. Example:
This would be easier to do with a frame subroutine that gives default values and requests only a name and title bar:

(define myframe (instantiate myframesubroutine% ("Hello World")))
(send myframe show #t)

I am looking for a way to write myframesubroutine% and use it to produce a window with these values:
(x 175)(y 175)(height 300)(width 600)

If anyone could help out with that, it would be much appreciated.