Getting a string to become a signal

So i'm trying the following.

When a user inserts a block into his model, the block will define the inputs of the block mask as a ASAP2 Signal. But, when i try to get a string (the signal name) into the input, the command get_param(gcb, '[insert variable name]') does not work. Instead of defining the string value, it defines "get_param" as an ASAP2 Signal.

Am i using the wrong command for getting the string, or am i overlooking something while using get_param?