[Jayz2K]

Well, just gave it a quick shot but it doesn't work.
Seems that the Keyboard popup entry is missing, or the getdirectory error ?.

You must use the same syntax as the normal skin settings, so providing the values in your skinsettings.xml file
That way you can also set the defaults with setting the optional attribute constantdefault="condition"

So, in skinsettings.xml:
<setting id="MyConstant" value="200" label="200" condition="" icon="" description="" constantdefault="true" />
<setting id="MyConstant" value="300" label="300" condition="" icon="" description="" />

And call the script:
RunScript(script.skin.helper.service,action=setskinconstant,setting=MyConstant,header=Width for Panel)

The includes file will be auto generated based on user selection and/or the defaults, no need for you to supply it.

If you want I can also add a prompt option so you supply some values and a way to enter manually, something like this:

<setting id="MyConstant" value="||PROMPTSTRING|||" label="300" condition="" icon="" description="" />
<setting id="MyConstant" value="||PROMPTNUMERIC|||" label="300" condition="" icon="" description="" />

Hehe, more clear now, missed the skinsettings.xml part :p This is going to be a large file Really intuitive to work in this one.

Yeah, the ||PROMPTNUMERIC|| is what I need
Not sure the ||PROMPTSTRING|| makes sense here since AFAIK constants are numeric only ... ?

Also, while you're on skin settings, I'm using this great stuff a lot also to just build a select box and use the <onselect> action. But in this case, the dummy string name writes a useless skinstring. Should it be possible to add a ||SKIPSTRING|| so it writes nothing ?