What you are doing here is not dynamic variable naming. You're assigning a new variable name from your already assigned data.
This example shows the dynamic variable naming and assigning values to the dynamically named variables (U and V):
eval(['V' num2str(jj) '= jj'])
eval(['U' num2str(jj) '= ' 'V' num2str(jj) '*jj'])
Which is NOT recommended to employ.
That is equivalent to:
This one is the recommended one.