Return the maximum value of a variable array C-plex

Question

I have tried to return the maximum value of the pbefore[t] array using maxl function, but it didn't work. is there any possible way to do it? Thanks in advance.

dvar float dvar float+ pbefore[t];

forall(h in Gwsystem,t in time)
    Gw == GW[h].Gwc* maxl(pbefore[t]);