you can find the dates between a start date and an end date by using a Script Unit, which contains the code for calculating the intermediate dates. For example, you could first calculate the number of days between the two dates received as input (e.g. start date = 10/10/12; end date = 10/14/12; number of days = 4). Secondly you could add single days to the start date, until you add all the difference days and you reach the end date (e.g. 10/10/12 + 1 = 10/11/12; 10/10/12 + 2 = 10/12/12 and so on).
To find the difference days between the start and the end date you can use the Groovy
Date ".minus" method, that subtracts a date from a another date (both dates are espressed in milliseconds). The difference has to be divided by the number of milliseconds in a day. As result, you get the number of days between two dates. For example:
#input Date startDate, Date endDate
def startDateMs = startDate.getTime()
def endDateMs = endDate.getTime()
def numberOfDays = (endDateMs.minus(startDateMs))/86400000
The intermediary dates, calculated by incrementing the start date, could be added to a list which is returned from the Script Unit and passed for example to a Create Unit (working on Entity B) that stores the dates. The Create Unit should have the "Bulk" property enabled, so it can perform multiple object creations at once.