As far as I know, there’s no way for UDK to do that. I think you would have to make a list of all of your functions and make a big ugly switch statement:
function CallFunctionFromString(string FunctionName)
{
switch(FunctionName)
{
case "Function1":
Function1();
return;
case "Function2":
Function2();
return;
case "Function3":
Function3();
return;
...
}
}