>If I use with 'empty(allt(crsrprc.comments))' in 'visiable' property I see the command button always.
>If I use with '!empty(allt(crsrprc.comments))' in 'visiable' property I DONT see the command button always.
>to bee sure I entered a command button on my form and I checkd if empty (allt(crsrprc.comments)) - sometimes I got a message empty and sometimes not empty.

Sounds like you have NOT changed the sparse property!