Rik,

thanks, yeah that is similar to what I want. In fact basically it, except it doesn't work for me.

I want to change the value of a property of an instance.

Can you access the property?

I think I am addressing it properly, and it doesn't come up with any

errors,

but when I check the property it hasn't changed.

If you have named propertysheets the manage_changeProperties won't work: then you'll have to point your method explicitly to the propertysheet.

could this be to do with permissions? or would I get an error then?

Yep, though not always (confusing eh?). Try executing it as the superuser, that way you'll always have the permission, unless you didn't set them in the class (assuming it's a ZClass, but in python products it's probably not much different) Then it would become something like (untested): <dtml-call "_.getitem('z958063364').propertysheets.<propertysheetname>.manage_changePro perties({'children' : 90})"> hth Rik