Hello,

I want to use a variable in a formula multiple times without having to enter the same values more than once. For example, the effective half-life of radionuclide after ingestion is defined as:

effectiveHalflife[physicalHalflife_, biologicalHalflife_] :=
(physicalHalflife * biologicalHalflife) / (physicalHalflife + biologicalHalflife)

The residual mass after some elapsed time then would be:

residualMass[n0_, time_, physicalHalflife_, biologicalHalflife_] :=
n0 * 0.5^(time/effectiveHalflife[physicalHalflife, biologicalHalflife])

I now want to build a widget of this formula, but I can't find out how to reuse physical- and biological halflife without having to enter these twice. Say I already have this template:

[//quantity:${ingestedMass}//] * 0.5^
 ([//quantity:${elapsedTime}//] / 
  ([//quantity:${phyHl}//] * [//quantity:${bioHl}//] / 
   ([//quantity:${phyHl}//] + [//quantity:${bioHl}//])
  )
 )

How would reuse phyHl and bioHl without having to enter these values twice?

Thanks, Alex.