如何正确显示数据库里同时存在的GB码和BIG5码？

public function checkbig(strsource as string) as boolean
dim idx as long
dim bytetemp() as byte
checkbig = false
for idx = 1 to len(strsource)
    bytetemp = strconv(mid(strsource, idx, 1), vbfromunicode)
    if ubound(bytetemp) > 0 then
        if (bytetemp(1) >= 64) and (bytetemp(1) <= 126) then
            checkbig = true
            exit for
        end if
    end if
next idx
end function