Validation rule for your conditions:
- RecordType
RecordType
= "Clinical Studies" - Status__c
Status__c
= "Draft" - Start_Date__c
Start_Date__c
&& End_Date__cEnd_Date__c
are changed. - Date_Change_Reason__c
Date_Change_Reason__c
should not be null.
AND(
$RecordType.Name = "Clinical Studies",
ISPICKVAL(Status__c,"Draft"),
ISCHANGED(Start_Date__c),
ISCHANGED(End_Date__c),
NOT(
ISBLANK(Date_Change_Reason__c)
)
)