loading external jpgs with url that contains a variable

Thx for your previous great help, my question now is this:

I've four buttons that load an external swf each.
The four swf are similar, except for the url of the jpgs they load.
I'd like to use a variable to change through the buttons that load swfs.
So if my url is "galleries/galleryone/1.jpg" with button one
And gellerytwo for button two etc etc
I'd like to have a variable myvariable=gallerytoload
so when I press button one myvariable=galleryone etc
And so far I'm able to write the code.


But... How can I write this on the url?
something like "galleries"+[myvariable]+"1.jpg"?
but it doesn't work
is it possible???

thx a lot