Passing a string to an expression in Access

[birdDBheadache]

I am trying to take the results of a subroutine (which is the string strFields in the code below) and pass them to an expression in an Access query. Is this even possible or am I thinking about this the wrong way? Can I only use functions in an expression?

Sub Fieldnames() 
    Dim Rst As Recordset
    Dim strFields As String
    Dim db As Database
    Dim f As Field
    Dim qdfParmQry As QueryDef
        Set db = CurrentDb()
        Set qdfParmQry = db.QueryDefs("qry_1test")
        qdfParmQry("Forms!Occu_formatting!Species") = [Forms]![Occu_formatting]![Species]
        Set Rst = qdfParmQry.OpenRecordset()
   
    For Each f In Rst.Fields
      strFields = strFields & f.Name & ", "
    Next
    Rst.Close

strFields = Left(strFields, Len(strFields) - 2)

End Sub

[GKJR]

I've read that one of the distinctions between functions and subroutines is that only functions can be called from a query. Couldn't you just change this sub to a function?

[birdDBheadache]

Ok that worked...now on to the next problem!

[NeoPa]

Good answer. Only function procedures (code that returns values) can be called from SQL. Sub procedures may not even be invoked from SQL so even if you want code to execute and don't care about the returned value, you still need a function if called from SQL.

NB. Queries are written in SQL.