Thanks for taking the time to read my question.

I have made a function in my Excel workbook, and can select it from the
Insert - Function - User Defined list. When you select it, the dialog box
comes up in which you can enter the parameters.

When you select a regular function, there is help on each input and a
description.

Example: VLookup Dialog box has

Lookup_value
Table_array
Col_index_num
Range_lookup

Below these is a description of the function, "Searches for a value in the
leftmost column of a table, and then..." and a description of the current
input. Lookup_value for example reads: "Lookup_value is the value to be
found in the first column..."

How can I get this on my own function?

I hope this makes sense. If not, I can try to explain again.

Thanks,

Brad