thegoodhen:
Yea, this seems ok to me. Just make R3 switchable for the different ranges and you're done. The configuration is a noninverting amplifier. The formula is:A=1+(R3/R2)
where A is the amplification coefficient.
Using that figure the values for R3 for different gains. Be careful about the rail-to-railness of the opamp (have a sufficient overhead, it won't give you 5V out with 5V rail...) and compensate the input offset, which also gets multiplied by your gain.
Edit: also don't make the gain crazy high, about 100 is max I'd go.
Would adding potentiometer as R3 work ?
Well I have some theoretical knowledge about the op amps ( amplification , inner resistance , etc.) , but could you be more specific on rail-to-railness I don't know much about it.