Attached is a VB6 code for creating a 64 bit double precision floating point value from a binary value stored as a string. It isn't especially efficient since it uses string conversions but it should work. I just added a wrapper function to convert 4 integer registers into binary so it can convert the whole binary string into a double.

For example, 1234567890.123456 in binary is: 0100000111010010011001011000000010110100100001111110011010110111
If you read that from a PLC as 4x 16-bit unsigned integers, they will be:
16850 (0100000111010010)
25984 (0110010110000000)
46215 (1011010010000111)
59063 (1110011010110111)

Call IntsToDouble(16850, 25984, 46215, 59063) and it will return 1234567890.123456 as a 64-bit REAL.

Released for:Schneider Electric South Africa