Urgent Dmax Help Required

Hello gentlemen,

My main form contains a Entry_No (Text – Not duplicate) field. I used following code in the same form in a command button’s OnClick event to increment integer value of Entry_No to “Issue-1”, Issue-2”, “Issue-3” & so on.

Dim strmax As String
strmax = DMax("[Entry_No]", "T_Drug_Receiv_Head")
Me!Entry_No = "Issue-" & Right(strmax, _
Len(strmax) - _
InStr(1, strmax, "-")) + 1

No problem with above code. It works fine.

The record source of the main form initially was based on query which I removed later. I placed following code to display only the last record while form opens (on Open event). This is a try due to very large table and I don’t want my form / query to load all 90,000 records into the memory at one time that takes time.
I placed a unbound text box (TxtMaxt) to disiplay Entry_No field of last record of the table which is ok.

Txtmax = DMax("[Entry_No]", "T_Drug_Receiv_Head") ‘ This is OK.

Dim NSSQL As String

NSSQL = "Select * from T_Drug_Receiv_Head where [Entry_No] = Txtmax"
Me.Form.RecordSource = NSSQL
Me.Refresh

When I open the form, it asks me ‘Enter parameter value’ for ‘Issue’. When enter something then dialog closes and form appears with blank record except showing displaying Entry_No field of last record of the table in the Txtmax unbound text box.

When I removes code from on open event and selects query that was set before as record set, it works.

Where might have gone wrong?

With kind regards,
Ashfaque