How to see if R returns a warning but won't output it to the screen?

Question

I was doing computation or C# and R.net. I would like to do the computations such that it won't output warnings or results to screen but saves them to the variables. I found that the C# won't output the result to the screen if I set engine.AutoPrint = false;I there something similar to warnings as the script outputs them automatically? Or is there some r-code such that

if f(data,param1) does not output a warning 
    output f(data,param1) 
else 
    output f(data,param2)

I tried options(warn=-1) but it did not solve my problem.