Off topic:how to replace r code inside function body

Question

[ycding]

I want to write a user defined function that I can replace part of R codes.

first, I ran the following code.

middle.pred.young <-PAMfunction(training=middle, met.status=middle$met, 
test=young, ....)
correlation.middle <-corfunction(middle.pred.young)
(more R code with different functions to process the file 
                 "middle.pred.young)

then, I replaced the word "middle" a few times to run the following codes;

old.pred.young <-PAMfunction(training=old, met.status=old$met, test=young, 
....)
correlation.old <-corfunction(old.pred.young)

then more similar code I need to run;

   all_age.pred.young <-PAMfunction(training=all_age, met.status=all_age$met, 
   test=young, ....)
   correlation.allage <-corfunction(all_age.pred.young)

so, I only need to replace one word. I would like to copy SAS macro idea in R.

   %macro predict;

   &age..pred.young <-PAMfunction(training=&age, met.status=&age.$met, 
                                    test=young, ....);
   correlation.&age <-corfunction(&age..pred.young);
        .....;
   %mend;

    %predict(age="old")
    %predict(age="middle")
    %predict(age="all_age")

Can you do me a great favor to write R function to do the repetitive job?

Thank you,

Ding