I have a small form with 4 textboxes on it linked to
A1
A2
A3

A4

The sheet is protected
They first 3 are linked to cells in the spreadsheet via the control
source property

The 4th textbox links to a the formula cell A4 with SUM(A1:A3) in it
The textbox is locked

When clicking into the 4th textbox excel throws the error "Exception
occurred"

By unprotecting the sheet with the workbook open event using the
userinterface parameter set to false
The exception error doesnt occur but then the formula gets lost from
the spreadsheet the first time
textbox 1 is entered
Any ideas

Thanks
Tony