Hi Clive
Assuming the cell you want to highlight contains a date, (A1 in this
example) then try highlighting your cell, then
Format>Conditional Formatting>dropdown to select Formula
is>=TODAY()-A1>30
Format>Select Font, Border or Patterns and colour to your choice.
The cell(s) in question to have the formatting, do(es) not neceesarily
have to hold the date, but obvioulsy the cell used as the reference
does.
You can combine things with for example
=AND(TODAY()-A1>=30,TODAY()-A1<90)
That could be one colour, and there are 2 more formats you can add to
have different colours for different date ranges.