Thread Subject: workspace input

I'd like to input from the workspace into simulink a single matrix with time as the first column and several columns of data following. However, when I try and use the data by referencing the columns (i.e. a=matrix(:,2), b=matrix(:,3), etc.), I get errors. What am I doing wrong? Thanks!

The error I'm getting is "Attempted to access variables(:,2); index out of bounds because numel(variables)=1." What happened to the rest of the data?