A variable position of a FvwmScript window?

My script starts like this:

WindowTitle     {Weather}
WindowSize      365 80
WindowPosition  0 0
Colorset        5

However, the next is not allowed:

WindowPosition  $[vp.width] 0

Basically I’d like to position the window according to the resolution of the monitor so that I wouldn’t have to edit the script if I change resolution. I’d like to use (Div $[vp.width] 2) or similar - centering the window. Is this possible at all?

You can use the script arguments to declare that width variable:

bleh = (GetScriptArgument 1)