Hello Sergey !
I tried your example with no success ??
Just to stupid ??? Just missing some basics ????

valid event of field in form
***********************************
p_data = alltrim(this.value)
p_table = "t_adressen"
p_field = "name1"
if p_cancel = .F. && no mouseclick on abort button so do the valid !!
return (p_exists(p_table,p_field,p_data))
endif
*********************************************

in my functions.prg i have it like this

function p_exists
parameters p_table,p_field,p_data
LOCAL lcSql
TEXT TO lcSql TEXTMERGE NOSHOW
SELECT count(*) as present from <> where <> = ?p_data
ENDTEXT
l_result = SQLEXEC(p_connection, lcSql)
if present = 0
return 1
else
return 0
endif

endfunc


There is an error at l_result = SQLEXEC(p_connection, lcSql)
invalid value,type or number of arguments
I think i missunderstood <>, <>

Please help

Best regards
Albert