How to auto update field on subform when field in main form is updated

[tamchar]

I have a form with subform. When the main form is generated the number series of document on field (Called RegNum), and I wont that number series is auto updated to field (called RegNumD) on subform. I develop my application whit access 2010.

Could you please help me to solve that requirement?
Thanks

[zmbd]

You have provided very little information about the overall table design and relationships.

If you need a value to change between the tables... normally that isn't a really a good thing to have the same information stored in multiple locations and you will need to think about the normalization of the the database if not the entire overall design.

However, if your talking about pulling related records between tables:

Normally, there is a parent/child relationship between the forms wherein as the information on the parent form changes, links cause the subform to change in sync.

you can also do this via vba using the update event

take a look at: 41.How to select Records in an Access Subform from a Combo Box

you also might be interested in Discussion: Advantages of a Subform vs. Filtering

[NeoPa]

If [RegNum] is a unique index of one table (on Main form) and [RegNumD] is a Foreign Key in another (on Sub form) and you want changes in [RegNum] to be reflected in [RegNumD]s automatically then you can set up a relationship between the two fields and ensure Referential Integrity is enabled for updates.

NB. This will effect these fields globally and is not a result of anything in either of the forms directly.