Thanks, sorry to be a pain but it doesn't work when i format the "merged" cell as date and time - the serial number still remains.
The workround i have is that the date and time in a1 & b1 are placed in "", which is ugly and, i guess, will not work when i use a pop-up calender.
my example is:
a1 b1 c1
08-Apr-03 16:05 377190.670138888888889
where c1 = =E1&""&F1
any ideas - Thanks ever so!