Perhaps this is what you need. I put binary/hex bytes into a string
this way. Snipped from my code:

Cmd is a command consisting of all hex bytes that I send out the serial
port.
pref & suff are prefix and suffix for the communications protocol

=======================================
Public Cmd As String
Public pref As String
Public suff As String
...
radio_address = CStr("&H" & ActiveSheet.Range("RadioAddressCell").Value)
suff = Chr(&HFD)
pref = Chr(&HFE) & Chr(&HFE) & Chr(radio_address) & Chr(&HE0)
...
Cmd = pref & Chr(&H5) & freq$ & suff
...
Cmd = Chr(&H16) & Chr(&H47)