[LOGic] Data type mismatch

[Sante - IK0HBN]

Hi guys,
may you help me in troubleshooting this error?
One step back....

Mauro, IK0CHU helped me at putting at work a report done by Hal, NN8L 
some years ago that I should use to print qso's direct on qsl card.
My card accepts till 4 qso's for card, so we were able to print them 
without problem, putting the FREQ read on the log directly on the card.

As I began with radio more than 20 years ago, old logging program did 
not save the frequency in the log itself, so Mauro put an expression 
that filled the missing frequency with the band, eg 20M, 15M and so on.

If I had only a qso with BAND printed on the card, everthing runs 
fine here, but if I have more than a qso to have printed on the card, 
if this /these qos's had the band to be printed too,
the result was having the first qso with the correct band on the 
card, and from the second to the fourth, if exist, having the same 
band of the first qso.
EG.
1 qso: 20M (OK)
2 qso: 15M (got printed 15M)
3 qso: 40M  got printed 15M).
As unable to fix the report, we thought to put a "static frequency" 
in all the FREQ field having care to respect bandplan, so:
1 qso on 14 CW, should write 14.000
1 qso on 14 RTTY , 14090
1 qso on ssb 14250,
so to force the report to print the frequency on the card. We use 
MASS CHANGE in ADVANCED
We did the following expression:
replace freq with "14.243" for BAND='20M' AND EMPTY(FREQ) AND MODE='SSTV'

but we got Data type Mismatch.
Any idea for both the problem or even the last one?
Thank you
Sante