Using feval on varying set of arguments

I'm using feval inside a function check_gradient. The setting is like this:

function iscorrect = check_gradient(f,grad,x0)

and feval as: feval(f,x0+del)-feval(f,x0).

But the thing is sometimes, I want to use feval inside my function check_gradient as

function iscorrect = check_gradient(f,grad,x0,b,mu,eps)

feval(f,x0+del,b,mu,eps)-feval(f,x0,b,mu,eps)

(I'm defining function handles 'f' that can take a varying number of arguments)

How do I factor in all such cases without defining a separate check_gradient function for each case?

Thanks a lot.