[R] adding to Trellis plot

[Hadassa Brunschwig]

Hello everyone
(Im not sure if i already posted this problem)
I have grouped data and i used a Trellis plot to show the curve of a fitted 
model for each group. Additionally i have a vector whose values are the 
highest points the curve can reach (the curve rises exponetially). Each 
value of the vector is the corresponding highest point for each group/plot. 
Now i want to show this highest point by adding to each plot a horizontal 
line. Obviously i should use panel.abline or something equal. How can i tell 
R that each value of this vector corresponds to the different plots in the 
Trellis plot?

Thanks a lot for answers

Dassy