run time error 3421

I am using VB6 and I am getting a run-time error. I want to but a debug code @ the cm7 that tells me what the var is at the time. I know what the part number is that it gets the code. I am new to VB6 but I know vb enough to follow code but I am working in a code that someone else created.

Here is a piece of the code:
' If isSolution Then
' cm7("PART") = sdb2 (The error message happens here)
'Set sol_desc = cm7.Execute
'If Not sol_desc.EOF Then
' srvrOld = RTrim(sol_desc("DESCRIPTIO"))

and cm7 code:

'This command gets the description to display on the solutions page
Set cm7 = CreateObject("ADODB.Command")
cm7.ActiveConnection = SprovenConnection
cm7.CommandText = "select descriptio from SPLIST where PART_NUMBE = ?"
cm7.CommandType = 1
cm7.Prepared = True
cm7.Parameters.Append cm7.CreateParameter("PART", 129, 1, 25)
cm7.CommandTimeout = 1000