Set Field  does NOT require the field to be on the layout.
I am not sure what you mean by "the desktop next to the layout".
RE: Next to the layout. I guess I should have said "next to the form" on the layout.
Sorry for the confusion and thanks for the input.
That's still confusing. The field is either on a layout or it's not. In either case, set field will work. I'd check your script and the data type of the field in question. Any chance you are trying to use set field to enter an expression like "3/15/09...3/25/09" into a date field? If so, that's your problem as that won't work in any case.
If you are trying to enter an expression into a date field via script while in find mode, you still have to use "insert text" or "Insert calculated result" and now have a layout sensitive script that won't work unless the field is present on the layout.
Another possibility: make sure you don't have the "restore" option selected in your Perform Find script step. This option will overwrite the values you entered with your Set Field.
Any chance you are trying to use set field to enter an expression like "3/15/09...3/25/09" into a date field? If so, that's your problem as that won't work in any case.
It WILL work in version 7 and above.
I made the jump from 5.5 to 10 and missed that one. I thought I had tested this one and found it still didn't work. However, I just did a quickie experiment and you are correct. Set Field can be used to enter text expressions into a date field when the layout is in find mode. That eliminates one more case of undesirable layout sensitivity in the scripts I've been updating since for the past two months.