Sorry, I guess I missed that the OP wants to modify windows registry items.
Some years ago, I looked into that. I have a note that says you need a support module called "REXXIO" Where you get that, I have no idea. It is mentioned at: http://www.edm2.com/index.php/REXXIO.
http://www.lestec.com.au/lestec/lestec.cgiIt looks like it is $14 to buy.
LesTecIO 4.0 - 257 Functions
LesTecIO contains most REXXIO REXX Input/Output functions and does not require MAID to be installed.
It is designed for people who require the functionality of REXXIO but do not need a GUI interface or do not have MAID installed. For details select a function.
V4.0 for Windows 7 Windows Vista Windows XP Windows 2000 Windows 95 Windows 98 Windows ME Windows NT 3.51 Windows NT 4.0
V3.1 for OS/2 2/0 or later (including OS/2 Warp 3.0, Warp Connect, Warp Server, and OS/2 Warp 4.0)
65 File Functions
14 Directory Functions
9 Search Functions
19 Window Functions
7 Keyboard/Mouse Event Functions
3 REXX Functions
5 Registry Functions
19 Global Stem Variable Functions
26 General Functions
9 Comms Functions
4 Event Functions
9 Internet Functions
54 Graphic Functions
7 Process Functions
2 Email Functions
5 Socket Functions