You need to use item states as in:

0010 BEGIN
0020 LET tv=100
0030 LIST_BOX tv,@(40,11,30,10),OPT="e|!",SEP="/"
0040 LET tv'statebitmaps$="!Emptybox|!CheckBox"
0050 LET tv'autostate=1
0060 WHILE 1
0070 READ DATA city$,prov$,END=*BREAK
0080 LET items$+="{;1}"+prov$+"/"+city$+SEP
0090 WEND
0100 LIST_BOX LOAD tv,items$
0110 ESCAPE
1000 ! 1000 - Data
1010 DATA "Toronto","Ontario"
1020 DATA "Montreal","Quebec"
1030 DATA "Calgary","Alberta"
1040 DATA "Ottawa","Ontario"
1050 DATA "Edmonton","Alberta"
1060 DATA "Winnipeg","Manitoba"
1070 DATA "Mississauga","Ontario"
1080 DATA "Vancouver","British Columbia"
1090 DATA "Brampton","Ontario"
1100 DATA "Hamilton","Ontario"
1110 DATA "Surrey","British Columbia"
1120 DATA "Quebec City","Quebec"
1130 DATA "Halifax","Nova Scotia"
1140 DATA "Laval","Quebec"
1150 DATA "London","Ontario"
1160 DATA "Markham","Ontario"
1170 DATA "Vaughan","Ontario"
1180 DATA "Gatineau","Quebec"
1190 DATA "Saskatoon","Saskatchewan"
1200 DATA "Kitchener","Ontario"
Basically you define the images to appear in front of the elements then assign a state to the elements you want to have images on. 

In the above I assigned two images (an empty check box and a checked one) then set every element with a state of 1 (the first image - emptybox). 

You can read and change each items state when they get clicked or use the Autostate property to have the control automatically change the state when clicked.

You can used the 'ItemState property to retrieve current state.

Is it possible to get a tree_view with check boxes next to the items(branches)?

The manual says something about 'cbx' but it seems to be for Webster starting with version 2023.

One quick thought -- which WindX are you using?
 
Is it possible you are using the 32 bit WindX and trying to run a 64 bit DLL (or vice-versa)?

Trying to use the HID.DLL through WindX and it just wont work (Linux Server)

Locally from pvx works great just cannot seem to work through windx even if I copy the code to the local PC and call "[lcl]scale.pvx",WEIGHT

I was able to create a Python program and Pvx just calls that to get the value.

I just cannot get a handler for it to return.  Is there way to get this to work?  Thank you.

LET HID_GUID$=DIM(16,$00$)
X=DLL("HID.DLL","HidD_GetHidGuid",HID_GUID$)
PRINT X

Global variables are only active within a session, not between sessions.

Follow up info...

I find that this works best on the more recent version (specifically Version 24) Windx Client.

A version 22 Windx Client still times out even though it is successfully executing the SET_PARAM '+A'=1 command.

I'm just curious about global variables.  I am setting a variable %my_variable$="Greg", but when I pull up a new window and do a ? %my_variable$ it is showing as empty.  Is there something else that needs to be set to define a global variable?  This is version 15.10.

I'm sorry, but off the top of my head I cannot remember which OpenSSL was supported by version 12.5.

Generally, on Linux, PxPlus uses the OS installed version of OpenSSL however there are changes within the OpenSSL interface that limit which version can be used without code changes within the PxPlus kernel.

PxPlus does not come with any source analysis scanning tools. I am also not aware of any from a 3rd party that support scanning PxPlus code. Then again we have not looked into this ourselves and don't know much about what is available.

If you find a tool that ends up being useful please share here as it may be useful to others.

While not accessing variables like request you can use *BROWSER within pxplus to execute JS and get the return of a JS function call or define or set a JS global variable.