This will require circular reference, an advanced feature.
For ease of testing, this example uses 5 second intervals
instead of whole days.
Your data might look like this:
Meas
88
When Monitor
3/29/2006 16:44:00 89.00
3/29/2006 16:44:05 90.00
3/29/2006 16:44:10 91.00
3/29/2006 16:44:15 92.00
3/29/2006 16:44:20 92.00
3/29/2006 16:44:25 93.00
3/29/2006 16:44:30 94.00
3/29/2006 16:44:35 95.00
3/29/2006 16:44:40 96.00
3/29/2006 16:44:45 97.00
3/29/2006 16:44:50 98.00
3/29/2006 16:44:55

Name the cell <Meas and the ranges <When, <Monitor.
Set Iterate to 1
Fill the <Monitor column with this formula
=IF(AND(NOW()=When,NOW()<When R[1]),Meas,Monitor)
It is written in R1C1 style.
For <When, select a time ahead when you might start a test.
During the 5 second interval between 16:44:00 and 16:44:05
you can enter data into <Meas and it will appear in <Monitor.
At 16:44:05, this value will be locked into the first row of <Monitor
and the next 5 second interval will be ready to sample <Meas.
After everything works, revert to A1 and change the interval to one day.