Toppers - Thank you for your comments and time. (For those new to the thread
see Rowsource in Properties Dialog 25 March.)

Exclamation marks aside, I have resolved the issue and in the interest of
courtesy and clarification I would make 2 constructive points:

1. Because
setting Sheet3!C2:C5 in the cboDriver RowSource Property Dialog OR
placing cboDriver.RowSource = "Sheet3!C2:C5" in the initialise event

resulted in Runtime Error 380 - Invalid Property Value, there had to be an
incorrect reference somewhere in the syntax. Enlightenment was provided by 2
posts:

The first by Dave Hawley Jul 8 2002 - in answer to a similar question he
offered and I quote:
ComboBox8.Rowsource="'" & sheet8.Name &"'!D2:D500"

The second included a dynamic range and was provided courtesy of Bob
Phillips Mar 23 2004 and I quote:
Me.ComboBox1.RowSource = "Sheet1!A4:A" &
Worksheets("Sheet1").Cells(Rows.Count, "A").End(xlUp).Row

What was missing therefore was a correct reference to the worksheet and
translating I found these worked:

setting DBase!C2:C5 in the cbodriver RowSource Property Dialog OR

placing in the initialise event either:
cboDriver.RowSource = "'" & Sheet3.Name & "'!C2:C5"" OR

cboDriver.RowSource = "DBase!C2:C" &
Worksheets("DBase").Cells(Rows.Count, "C").End(xlUp).Row

2. Using these solutions I experimented with RowSource and was able to
determine that code placed in the initialise event DID supercede property
values set in the Dialog Box. This continues to support my earlier
contention of same.

Again, thank you for your time and comments in a group which I have always
found helpful.

Geoff