Hi Riaang,
Set the second form's recordsource to a query. Have the query contain the same table the form should normaly edit, but set the criteria field of the user field to the control on the first form that contains the users name.
To do this, open both forms, then create a query in design view. Add the table of interest to the query, and set the criteria for the user field to the control that contains the user's name on the first form. Right click on the criteria field and select "build" and use the expression builder to find this control if you need help with the syntax.
I would then have a button on the first form that opens the second form, and when pressed. Since this second form looks for the use's name from this first form, when the second form is opened, it's record source will only be the records relating to the user specified in the first form.
You might need to lock the control holding the user name in the first form when they press the button to open the second form, so they don't go and change it. You could unlock when they close the second form.
HTH,