Populate a cck link field

Hi

I want to use Rules to populate a cck field and am having trouble when the field is a CCK link field.

I have two content types each containing the same CCK link field. I want to set up a Rule that populates one of those cck fields with the value of the other one. I want it to trigger when the first content type is updated.

I have been able to do this easily when I specific a fixed link value to write into the second field. However when I try and use a token it does not work for some reason. I am trying to use php to populate the field with the token. I have been able to do that for text cck fields and date cck fields but it is not working for this cck link field.

Any ideas? If you know how to do it and would post the php required that would be great. Thanks for any help.