How to generate random number in excel

=CONCATENATE(
IF(INT(RAND()*2)=0,CHAR(INT(RAND()*9+48)),IF(INT(RAND()*2)=0,CHAR(INT(RAND()*25+65)),CHAR(INT(RAND()*25+97)))),
IF(INT(RAND()*2)=0,CHAR(INT(RAND()*9+48)),IF(INT(RAND()*2)=0,CHAR(INT(RAND()*25+65)),CHAR(INT(RAND()*25+97)))),
IF(INT(RAND()*2)=0,CHAR(INT(RAND()*9+48)),IF(INT(RAND()*2)=0,CHAR(INT(RAND()*25+65)))),
IF(INT(RAND()*2)=0,CHAR(INT(RAND()*9+48)),IF(INT(RAND()*2)=0,CHAR(INT(RAND()*25+65)))),
IF(INT(RAND()*2)=0,CHAR(INT(RAND()*9+48)),IF(INT(RAND()*2)=0,CHAR(INT(RAND()*25+65)))),
IF(INT(RAND()*2)=0,CHAR(INT(RAND()*9+48)),IF(INT(RAND()*2)=0,CHAR(INT(RAND()*25+65)))),
IF(INT(RAND()*2)=0,CHAR(INT(RAND()*9+48)),IF(INT(RAND()*2)=0,CHAR(INT(RAND()*25+65)))),
IF(INT(RAND()*2)=0,CHAR(INT(RAND()*9+48)),IF(INT(RAND()*2)=0,CHAR(INT(RAND()*25+65)),CHAR(INT(RAND()*25+97)))),
IF(INT(RAND()*2)=0,CHAR(INT(RAND()*9+48)),IF(INT(RAND()*2)=0,CHAR(INT(RAND()*25+65)),CHAR(INT(RAND()*25+97)))),
)

 

this will genereate    between 4 to 22   chars .