You can insert any form you want. It can also be a continuous form, another table or Query. It's not necessary that the table or query is linked to the main datasheet table/query.
Make a datasheet form (i used the wizard for this test)
You select the controls in design view, right click select layout > tabular. Right click on the first control, right click > Insert Below > Click on the empty cell > Properties > SourceObject and select any form, table, query you want.
Have fun with it.
You can do this also by code, but I just made this discovery a few minutes ago. May be you can post some usefull usage of this trick.