In the current event of the subform, set the Enabled property of the Planned
Start Date control in the sub form based on whether the Planned Start Date
in the main form has a value:

Me.MySubformControlName.Form!txtPlannedStartDate.E nabled = Not
IsNull(Me.txtPlannedStartDate)

"Marc T" wrote in message
...
Hi again,

a bit of a steep learning curve for me so far!

What I have is a form with one set of fields such as:
Doc No, Doc Rev & Planned Start Date

and a subform with fields such as:
Transmittal, Status, Planned Start Date

As you can see, the Planned Start Date appears on both (from different
tables). The subform data is editable. What I'm trying to do is set a
conditional format of disabled to the subform field if the main form's
field
contains a value...

E.g.

main form has:

Doc No Doc Rev Planned Start Date
0001 A 31/10/09

Subform has

Transmittal Status Planned Start Date
00-001 Pre (greyed out)

I've tried a few different expressions with no joy. Any ideas on how to go
about this?

Thanks as ever,
Marc