Struggled for a while on this problem and hopefully you can help...  I have a mathematical expression that currently has a symbol where I used to have a function variable.  How do I make the symbol back into a variable, so that my expression becomes a function again?  My function became an expression when I saved it in a matrix, and so now I'm trying to make the different matrix elements back into functions after having constructed the matrix.  Thanks in advance.

>INCLUDING SOME CODE (my first time contributing on this website...)

Imagine a For loop sum (I've removed a substantial amount of code that's irrelevant for now)

    Pstatesalpha[λ_]={};
    For[jsum = 1, jsum <= 3, jsum++,(
    Pstatesalpha[λ_] = (delem*a0)^2*SumPstatesalpha[λ] + Pstatesalpha[λ];
    AppendTo[RankMatrix, {Alpharank,Pstatesalpha[λ]}])

Note that I've saved    Pstatesalpha[λ] 
as a function into     `RankMatrix`.
When I want to access (for instance) 

    RankMatrix[[1,2]]

Mathematica returns an expression that includes $\lambda$, but I can't use it as a function anymore.