8.5 Formula error at runtime

Hi

My client is getting the following error message
Error in formula <check>.
'If not IsNull({@.sApplicant2}) Then
'
A number, currency amount, boolean or string is expected here.
The error box is entitled 'Print Engine Error'

This is from a compiled 8.5 executable I created for him.
It runs fine on my machine and on the server I posted it up on for him.
We checked his schema.ini, his text driver and the exe and they are the same as what I have. I copied over the data files he generated that were used for the report and they work on my machine.

This error looks more like a development type error.
I would have expected this type of error to morel iley occur if I did a print preview during design time or tried to compile in the design environment.
I have a failry simple formula parameter called check in a sub report that seems correct and as I said the report runs fine on my machine.

Anybody have any ideas on what the problem might be and where to look?

Much obliged
Paulwhat data type {@.sApplicant2} is?|||Hi

{@.sApplicant2} is a formula.
So, I don't use a Dim statement or other declaration statement for it.
I haven't specified its datatype, so I suppose it is the default datatype, whatever that may be.
The fields I use with it to set its value are strings.
Pretty much everything on the report is a string, except for some simple date fields not referenced by any formulas.
There are no numerical calculations being performed in the report.

Thanks
Paul