Auto fill a field in unbound sub-form datasheet

[peterbites]

Hi, Programmers I'm Creating a database app for where I work to track plant wear and hopefully use the data to predict plant breakdowns before they happen.
I have a form that contains a sub form & datasheet that is created from SQL query, which is in turn created by selections in three combo boxes on the master form. Which I have got to work exactly as planned.
The Problem is only when I wish to add a new record to the datasheet, there is a foreign key field at the start of the new record I want to auto fill with the "ID" value that is available in a combo box on the master form.

Question: How do I progammatically set the value of that "id"field with the numeric value from the combo box.
Sorry I'm new here so hope this is clear for you.
Thanks

[peterbites]

Ok I solved this myself,well close enough.
I made a Variable, moved to the acPrevious record in datasheet
set my variable = required field in that record
then moved to acNext record and set that field = my variable.This works ok as long as there actually is at least one previous record for that item.

[jforbes]

I'm not 100% of what you were/are doing, but this should be some helpful information for you:Refer to Form and Subform properties and controls

So if your situation was one where you wanted to Default a value on the Subform to a value on the MainForm, you could set the Subform Field's Default property to something like:

=[Me].[Parent].[RecordSource].[SomeID]

and then the value of SomeID from the Parent Form will be put on the all the new records. There are more elegant ways of doing this, but this demonstrates the basic idea.