How to store value into variable which is as value of another variable?

[chromos]

I am not sure if I can explain it understandably...

I cannot store value into variable directly because I don't know its name. But I know that its name is stored in other known variable.

For example:
I have something like this: L1(1):="VarNameChoosenByUserViaInput";
I can view value stored in VarNameChoosenByUserViaInput with EXPR(L1(1)), but how I can change value in that variable via L1(1) indirectly?

Thanks for any advice.