Initial value from a specific column of the last row of table....but filter results by the Ref

[Driller]

I have a table called Boreholes

Each borehole can have one or many Drilling Methods, which is a table ref by the [Borehole].[Unique_ID],

Each time i create a new Drilling methods row, i want the initial value of column [start depth] to be the LAST entry in the [finish depth] column where the [borehole] is the same. If it is the first entry then blank.

Is this possible? Do i make sense even?

[Suvrutt_Gurjar]

If you could elaborate a bit more about the relevant column names in respective tables, then the community could help you better. are the columns [finish depth] and [Start depth] in the drilling Methods table? Is the Drilling Methods table the child table of the Boreholes table?

[Driller]

Yes sorry. Correct, the start depth and finish depth column are both in the drilling methods table which is a child of the borehole table. 

[Suvrutt_Gurjar]

Thank you. Such multirow expressions to search a value based on some criteria can be sync time expensive. Please explore below.

In the Borehole table , please create a VC called say [Related Finish Depths] with an expression something like 

[Related Drilling Methods][Finish Depth]

where [Related Drilling Methods] is the system generated reverse reference column in the Borehole table.

Now in the initial value of the [Start depth] column in the Drilling Methods table, please have an expression something like 

INDEX([Ref Column name that references Borehole table in the Drilling Methods Table].[Related Finish Depths],COUNT([Ref Column name that references Borehole table in the Drilling Methods Table].[Related Finish Depths]))

Please test well.