Which field is being changed, the field that serves as a key field in the relationship or a data field that is looked up or displayed from the related field?
I think this is what you are asking here:
You have a relationship between two tables: Table1::KeyField1 = Table2::KeyField2
You want a change to KeyField1 to update KeyField2 in all matching records in Table 2.
If so, best solution is to design your relationships so as to make such updates unecessary, especially since a cascading update feature is not available in FileMaker like it is in some other products. (Even when you have this feature, it's best not to use it as the cascading update can trigger a significant delay as many, possibly hundreds or thousands of related records update.
To do this in FileMaker requires scripting and the use of ScriptTriggers can make the process automatic.
Use an OnObjectEnter trigger on KeyField1 that passes the current value of KeyField1 as a parameter to a script that stores that value in a global variable: Set Variable [$$OldValue ; Value: Get ( ScriptParameter ) ]
On OnObjectExit or OnObjectSave triggered script can then do this:
Set Variable [$NewValue ; Table1::KeyField1]
Set Field [Table1::KeyField1; Value: $$OldValue ]
IF [ Not IsEmpty ( Table2::KeyField2 ) // there are related records to update ]
Go To Related Record [Show only related records; From table: Table2; Using layout: "Table2" (Table2)]
Replace Field Contents [no dialog; Table2::KeyField2 ; $NewValue]
Go To Layout [original layout]
Set Field [Table1::KeyField1 ; $NewValue ]
Note: if this takes place on a multi-user system and another user has opened (locked) one of the related Table2 records, that record will not be updated by the Replace Field Contents step and an error will be thrown.
my situation is :
the two table are linked by the field1 (the code of a plate) and the fields are the code of the Automotive pieces avaiable for that product. in the table 2 the code of the product is unique
But what change are we talking about here?
Do you want to change field2 in table2 and see the same change in table1? (Or the opposite)
If so you should remove Fields 2 through 6 from one of the two tables and just use the one set of fields any where you need to see or edit this data. Since the data is only in one place, any changes made automatically appear on all layouts and reports.
Here's an example.
To replace fields 2 through 6 in table 1 with the related fields from Table 2:
In every layout where these fields were found, enter layout mode and double click each such field from table 1 to bring up the specify fields dialog. Select Table 2 from the drop down at the top of the dialog. Then select the corresponding field from Table 2.
Once you have done this in every layout where fields 2 through 6 were found, open Manage | Database | Fields and delete these field definitions.
Note: It's very possible that a better design for your database is to place fields 2 through 6 in separate related records instead of all in the same record like you have.
unfortunately I can't do this because could be changes in every record in the table1, so I've decided to abandon this way