Continued...
Phase 2: Create Relationship & Create Related Month Helper(this will assume you have a field called [Project Approval Date], and I will use that, if you have other "Date" fields that you are looking to track, you will need to duplicate this phase for those other dates.
Step 1:
Create the relationship where each month has many projects.
(if you do end up making more relationships you will want to name this relationship appropriately, [Related Project Approval Month], for example)
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You'll notice that you have a dropdown to manually connect the project to a month (we will make that automatic below)
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Step 2:
Create a "Helper" field on the Project table. It will be a formula-text field.
Call it something like [Related Approval Month Helper]
Step 3:
Use the same formula you used for the Month Helper, with one modification.
You will need to convert the date to the first day of the month, then use the syntax to match the other "Helper" fields.
Like so:
ToText(Year(FirstDayOfMonth([Project Approval Date])))&"-"&Right(ToText(Month(FirstDayOfMonth([Project Approval Date]))+100),2)
Step 4:
Change the Reference field to a formula-text field.
Change the field type [Related Project Approval Date] field to formula text.
In the formula entry box, simply reference the [Related Approval Month Helper].
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Now your relationship is automatically connected
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You can now make any summaries and lookups you need to.