Your tables should look like:
TblVendor
VendorID
VendorName
etc
TblPart
PartID
VendorID
PartNum
PartDesc
etc
Create a query named QryVendor based on TblVendor. Make VendorID the first
field in the query and VendorName the second field. Sort ascending on
VendorName.
Create a query named QryFrmPart based on TblPart. Sort ascending on PartNum.
Put the following expression in the criteria of VendorID.
Forms!FrmPart!VendorID
Create a continuous form. Name your form FrmPart. Your form should be a
continuous form so you get a list. Base the form on QryFrmPart. Add an
unbound combobox in the form header. Name the combobox VendorID. Set the
Rowsource property of the combobox to QryVendor. Set the Bound Column to 1,
Column Count to 2 and Column Width to 0;2. Put the following code in the
AfterUpdate event of the combobox:
Me.Requery.