Help needed on Force Sensitive Resistor

Hello,
Am new to arduino and ee! coming to the point, am building a smaller version of AGV for my project!and it needs to lift a weight and differentiate between weights! ex:400gms and 800gms!
Load cell was the first option,but its ruled out because its way too big for my bot!
so,can i use a Force Sensitive Resistor to differentiate betweeen weights ????(need no values or accuracy!,just the ranges!!)
can i use arduino for this?

Can you paste a few links in your text ?
What is AVG ? Which load cell are you looking at ?

My first thougth was: "Load cell" or "force sensor".
Aren't there any small ones ?
Search for "miniature load cell" and "subminature load cell".

A Force Sensitive Resistor should be possible. But 400g could be already to much for a simple force resistor.

Perhaps you can measure the current of the motor while lifting.
In the past I made my own force sensor with a bicycle inner tube between copper. The carbon in the the inner tube had a resistance which depends on the pressure.

Erdin:
A Force Sensitive Resistor should be possible. But 400g could be already to much for a simple force resistor.

Well according to sparkfun, their small one can sense from 100g up to 10kg. It says it shouldn't be used as a scale, but I imagine it can be used for gross sensing and could probably distinguish between 400g and 800g.