At a first glance, I don't know if that's a typo, but check
Let rowlimit = NoOfRows('DataTable'); // table needs to be single quoted
EDIT: Apart from that, you need to specify RESIDENT instead of FROM when loading from DataTable:
Table2: Load col2,col3 RESIDENT DataTable;
FROM keyword is intended to sources external to qlikview. RESIDENT means loading from an already previously loaded table, that is the case.
Hope that helps.