Function that converts an expression into a boolean ( -1 / 0 ).
Syntax
      CBool (expression)
The keywords True and False are predefined constants and are interchangeable with the values –1 and 0, respectively.
Example
Dim boolExStaff
boolExStaff = CBool( Me!chkExStaff)
“The aim of science is not to open the door to infinite wisdom but to set a limit to infinite error” ~ Bertolt Brecht ‘Life of Galileo’
Related:
CByte - Convert to byte 
CCur - Convert to currency (number) 
CDate - Convert to Date 
CDbl - Convert to Double (number) 
CDec - Convert to Decimal (number) 
CInt - Convert to Integer (number) 
CLng - Convert to Long (number)
Nz - Detect a NULL value or Zero Length string.