Tom,
You pass a parameter to the fomr that contains the combobox. The form receives the parameter in its Init event, you need a PARAMETERS or LPARAMETERS statement in the form's Init. If the parameter you pass is the name of the alias to populate the combo you can do something like this in the Init of the form;
LPARAMETERS pcAliasForCombo
Thisform.Combo1.RowSource = pcAliasForCombo
Thisform.Combo1.Requery()