How do I replace "#Type!" with "?" in relevant field?

Using Access 2010, in limited field space on a report, I have reduced relevant name of volunteer offering assistance to first-name & first-letter-of-last-name with the following:-

=[txtHelpFName] & " " & Left([txtHelpLName],1)

All works well when the volunteer details have been provided or known. When they are not available, the field populates with "#Type!", which I would like to modify with a simple "?"

Any suggestions on how this can be achieved? Would an IIF Function work, using the above for the TRUE component of the statement?

Thank you...

How do I replace "#Type!" with "?" in relevant field?