make: target-depending prerequisites?

Hi,

I am trying to make the prerequisites of a target depend on the current 
target by taking into account the current value of %.
In the example below, I have a main (tex) file, with dependencies on a 
number of included files. These dependencies are indicated in variables 
with the name of the main file, with '_depend' appended to them. My 
strategy is then to create a variable DEPEND, depending on %.pdf, which 
contains the name of the variable that contains these dependencies, and 
use this variable in the prerequisites.
Unfortunately, this does not seem to work: $($(DEPEND)) does contain the 
right dependency, yet it does not seem to be present in the 
prerequisites. As a result, 'touching' the dependency does not trigger a 
rebuild when I run make for the second time.
What might I be going wrong and/or is what I want to do even possible?

Many thanks!
Yves


<-- Makefile -->

texfiles = main.tex

main_depend = section1.tex

all_pdf = $(texfiles:.tex=.pdf)

all: $(all_pdf)

%.pdf: DEPEND = $(@:.pdf=)_depend
%.pdf: %.tex $($(DEPEND))
	@echo "Extra dependencies:" $($(DEPEND))
	@echo "All prerequisites:" $^
	touch $@
	touch $($(DEPEND))


<-- end Makefile --->