DaveMoore wrote...
My spreadsheet has many worksheets (tabs) labelled like (e.g.)
61900003.
There is also a Summary worksheet with a column (D) containing all
those worksheet names. In an adjoining column (E) I wish to enter a
formula like ='61900003'!L5 with the worksheet name being gained from
pointing at column D.
that sounds as clear as mud! Perhaps my forlorn attempt will help.
='TEXT(D16,text)'!L5
....

You need to use the INDIRECT function. Try replacing your formula
above with

=INDIRECT("'"&D16&"'!"&CELL("Address",L5))