Counting field over Four Date columns if the field has value in the four coloumns

[dinaabdelhakam]

Hello There I have Field which states the Case ID whether its ACTIVE , RESOLVED, PENDING or CLOSED I need to count each case ID over four fields for OPEN_DATE, CLOSED_DATE, RESOLVED_DATE...etc if any case have the four dates it will be counted over them all
How can I do that ??