none of the Large tables are related
Actually they are, but under different names. The boxes found in Manage | Database | Relationships are not actual tables, they are table occurrences. Each "box" refers to a specific table found on the tables tab of manage database. If you hover the mouse over the upper left corner of these boxes, the data source table--the real table from the tables tab will appear and you'll find that there are fewer tables in this starter solution than you have boxes here because the same table is part of more than one relationship, but using different table occurrence boxes.
Specify Calculation shows to Evaluate this calculation from the context of the History Contact ID (I am assuming it is because that is where my due date is at at the moment
Unless a contact is limited to checking out only one item and cannot check out any other items until it is returned, the due date should not be defined in the contact table. Instead, it should be defined in the History table--which would be the purpose of the Due Date date field found in this table.
Case ( Left ( Assets::AssetsItem ; 3 ) = "LITK" ; 21 ;
Left ( Assets::AssetsItem ; 4 ) = "SPED" ; 14 ;
45 ) + Get ( CurrentDate )
Would compute the due date. This could be an auto-entered date calculation defined for Check In Date in the History table. To add an auto-enter calculation, find Check in Date in Manage | Database | Fields and double click it. Then click the auto-enter tab. Then click the calculation option. This date will be computed at the time a new History record is created--which records the date an asset was checked out and will then compute its due date.
But I think you need to look over an original copy of the asset lending library solution and figure out how the table occurrences work first.
Newbie asking stupid questions but:
(Left, is that meaning you want to start to the left and count over 3? If not counting what is the number 3 & 4 used for?
do I not need to show the 21 added to check out date?
The 45)+Get (Currentate) will that take the OT and the AT into account and add 45 days to the return date?
no, the staff can check out multiple items at once.
Thanks for your help, shall give it a shot in the morning when back at work.
Case evaluates to select the specified value (or calculation) paired with the first boolean expression that evaluates as "True". In this example, case will return one of three values 21, 14 or 45. Whichever of those three values that is returned will be added to the current date--which should be the same as your check out date--so you can use that instead of Get ( currentdate ) and just make this a regular calculation field instead of auto-entered if you want.