Prevent Duplication Records

[mubi_masti]

I have developed a database which is competible for web.

In this database, i have many tables but i m just sharing the common problem facing with other tables as well

For example
Table A (master tbl) and Table B (Details tbl) are linked with 1 to many relationship through lookup wizard.

tbl b has five fields and i need unique records for field1,field2 and field3. I have developed data macro for beforechange event for tbl B but that macro is not working properly. if there is duplication, macro generates msg and even i change the values to produce unique values still msg of duplication appears.

this kind of macro works excellant with stand alone single tbl but with linked tables the error appears continounsly

Can any body help me where i m doing wrong

 

[mubi_masti]

Thanks dear Hartman for your reply

I have not uploaded my database on any SharePoint yet, currently i m running it in JET/ACE environment.

I have linked both tables with numeric fields and there is no possibility that i get text.

I have developed data macro in which i lookup record in a table B with where condition.

Can you help me in sorting my problem. I have attached my db.

You can open Main form, in MDB subform, when you will add activity a error massage appear. I want to solve that error. Please help me out in this situation.

 

[mubi_masti]

is there anybody who can help me out in this situation.