Dynamic Compont Ceiling Error?

[jshal]

I have a problem creating a simple dynamic component. It is a square, where the user enters the square meters of this square. The X-value can be changed manually, so that the Y-value changes accordingly. The units in the model are in meters.

Size
LenX=ceiling(current("LenX"),30)
LenY=ceiling(Area*10000/LenX,30)

Behaviors
ScaleTool: Scale along red. (X)
Custom
Area (User imput in m^2), Units:Text, Users can edit as an textbox, Display in: Whole Number

The problem is that with the scale tool, the final X-value changes randomly.
When I remove LenX=ceiling(current("LenX"),30), the square behaves normally, but I want the X and Y value incremental every 300mm. Does anybody have a solution? TIA!

See model: http://jshal.site88.net/wp-content/uploads/2009/07/dc_room.skp