I am trying to model a function of observed data in JAGS. For example

   x[i,t]/phi ~ dpois(mu)

where x is observed and phi is a parameter in the model. I can't seem to get this working and am wondering if I may be missing some larger issue in JAGS. I am pretty sure you can't have any transformation of the data in the model statement and need to use a data block but that doesn't seem to be dynamic, thus not allowing for me to fit phi.

Any ideas?