If I switch forms from multiple categories to sub categories my listing are not displayed. If switch back I can see them. I have check the parameters of both forms and they are the same. What could I be doing wrong?

In regards to your question on changing forms, you did it correctly.

When XMod saves records it attaches the Form Id from the kb_xmod_forms table for the form that was used to enter the existing listings.

Changing forms in Configure Xmod Module will be a different Form ID and no existing records will be attached.

Multiple Categories:

It has been attempted by clients in the past.

It seems to confuse the user a bit when you have too many category options.

You can select multiple categories but the last category you select will need to be the one that you attach sub categories to.

Sub Categories can only be assigned to one category.

To make this change, you would need to modify the cboCategory form field.

The cboCategory field would be similar to the field on the Multiple Category Form except it is set to a Multi-Select List Box vs Checkbox list.

You would need to change the Xmod form control from Select1 to Select.

Make sure to change both the opening and closing select tags.

Note: Save your existing code to NotePad before editing forms and templates.

Reference:

Xmod Online Help

Xmod Select Form Control

Xmod Select1 Form Control

Yes it would seem confusing to the user. My situation made me reconsider how my categories are organized and I think I have found a way to use your sub category form as is. My categories are setup as catlevel1, catlevel2, then catlevel3. If a user chooses a catlevel1 and multiple catlevel2s this should work only I need some way to describe to the user that catlevel2 is for such things as catlevel3. Use catlevel3 as a description of catlevel2 as apposed to a sub category. Any ideas?

Sample:

Apparel & Accessories

Clothing - General

Clothing & Accessories-Retail-Men

Accessories

Belts-Apparel

The user would then select Apparel & Accessories as the main category and multi select both Clothing - General and Accessories as sub-category. If as they make their selection of a sub-category they could see a description of sub-categor it would be helpful.