Base64 conversion

Hello.
I want a converter for base64 numbers.
Standard base64's digits is 0-9 A-Z a-z and + and /
but the last two digits not in sort order, so these type of base64 numbers are not sort-able.
Mine is 0-9 A-Z a-z and { and }
the last two chars "{" and "}" are in correct sort order.
The main decimal number is separated in 6-bit digits. Each digit is shown with one of those 64 digits, listed above.
e.g. "h2Ht" equals to 732701815.
I did write it in Excel, but it's better it be in this site.

Thank you.