How would I write the following if statements in Splunk?

[troy44112]

How would I write the following statements in Splunk?
Variables are start_access and last_access

Statement
If 20 days have passed from the start_access AND there was no last_access since the last start_access, then the result is not active.

[ITWhisperer]

| stats latest(_time) as _time latest(access) as access
| where access="start_access" AND now()-_time > (20*24*60*60)
| eval result="not active"