When a grid has writeback enabled, you can use the format sheet and other Custom Format Areas to change and lock the grid cells.

Data entry mode is turned on on an Anaplan XL grid by selecting the Enable Writeback checkbox in the Grid Properties window.

If you're using writeback formulas, XL3LookupRW or XL3DoWriteback, you also need to enable data entry mode at the workbook level from the Anaplan XL > Options > Workbook Options menu item, in the writeback tab.

Please refer to the writeback page for further details.