2.5TDI rocker arm change without removing cams

Hello all,
I was just wondering if it is possible to change the lifter, pad and rocker arm without removing the camshafts? Isn't it possible to replace the lifter, push it in with something and place rocker arm between the lifter and camshaft?
I have 2 rocker arms missing and the lifter tip seems like it has a hole in it. I'm not planning to change the whole upper kit yet, but just replace two rocker arms since I'm going to change rocker cover gasket.

Best regards

I can’t see how you could do this except without a very big hammer...