[R] using function instead of formula in plm

[Erich STRIESSNIG]

Hi all,

I am trying to use plm to estimate coefficients in a model consisting of a
system of equations. So far I used mle2 from the package "bbmle", but now I
need to test for autocorrelation and mle2 does not provide for the necessary
tests. mle2 needs a 'function' as input that might as well consist of many
different equations. plm however requires an object of class 'formula' that
needs to be included in the plm-call. Does anyone know if there is a way to
make R understand that it should do something like

result <- plm(function,data = paneldata,...)

and what the object 'function' then has to look like in order to do the same
thing as an object of class 'formula' would do in the same place?

Thanks in advance, 
Erich