Reseverved Status for "CallInputString"?

Yesterday I downloaded R2013a. One of my scripts uses another script function named "CallInputString" defined as

function y=CallInputString(y,'enter y');

I get the following message whenever my main script tries to use it.

>> CallInputString

License checkout failed. License Manager Error -5 Cannot find a license for Optimization_Toolbox.

Troubleshoot this issue by visiting: http://www.mathworks.com/support/lme/R2013a/5

Diagnostic Information: Feature: Optimization_Toolbox License path: C:\Users\David\AppData\Roaming\MathWorks\MATLAB\R2013a_licenses\license_David-PC_521792_R2013a.lic;C:\Program Files\MATLAB\R2013a\licenses\license.dat;C:\Program Files\MATLAB\R2013a\licenses Licensing error: -5,357.

Is "CallInputString" a reserved variable name that generates that error?

I changed the name to "CallInputChar" and I had no problem.

Thanks.