vairable name as value of another variable, ASP classic

Question

i would like to make a function that takes the variable name as a string, check if exist a querystring, or a request.form or a variable with that name and return the value.

function revalue(varName)

   if request(varName) <> "" then
        revalue= request(varName)
    else        
        revalue= "" 
    end if

end function

how can i check if the variable called as the value of varName exist and has a value?

Answer 1

...

else
   if eval(varName) <> "" then
     revalue= eval(varName)
   else
     revalue= ""    
   end if
end if