Thanks Logit,

I have got the spreadsheet to work as you have instructed but the functionality is not as I require it.

The purpose of the black cell is that it will be used as an observation set separator that the user will specify.

The data will then be read into Matlab for manipulation and reduction based on the users input through iterations.

Is there a way to allow the user to set the cell to black (through the dropdown list) rather than having them pre-set to black then require changing (overwrite)?

This is also important for the usability in the Matlab program.

Thankyou in advance.