Depending on how you need it to evaluate and update, you may be able to keep it as a number field and specify an auto-enter calculation in field options. Adding or changing an auto-enter calculation does not automatically update the value in the field of existing records.
Thanks will try it.
Tried this, it auto evaluates before I create a record and I have to clear contents and re enter dates very slow and tedious for the user.
I have dateIn and dateOut entered with a drop down calendar
My calculation is DateOut - DateIn
This result is then used to calculate a price elsewhere....... i.e. a cost for a number of days stayed in our marina
Until now we have manually entered the number of days.
Did you clear the "do not replace existing value" check box?
then, as long as the fields referenced in the calculation come from the same record as the field with the auto-enter calculation, any change to DAteOut or DateIn will cause the auto-enter calculation to update.