Problem with transport of diluted species module

Hello,

I'm trying to use the boundary flux variable of the module in other modules, so to specify a flux in another module, the problem comes when I look at the equation of the flux:

tds.bndFlux_cA=if(r>0.001/sqrt(sqrt(mean(emetric2))) ,-0.5*(dflux_spatial(cA) )/(pi*r),NaN)

The problem is that during a certain time at the beginning the condition of r> is not true, and then my model cannot be evaluated. So I cannot use this expression in other modules.

So I have tried to copy that expression in variables and changing 0.001 for eps, but I receive a message error saying that it cannot be evaluated.

So the question is How can I use the boundary flux in other modules?

Thanks for all