vb.net 2003 crystal report add sum total in one field

[GIGAM25]

hi guys!

i generated a report using crystal report on vb.net 2003 from a dataset. there are 2 columns in it. name and amount. like this one,

name amount
gigam 100.00
hershey 300.00
tony 97.00

my concern is: i want to have a total below the amount. like this:

name amount
gigam 100.00
hershey 300.00
tony 97.50

497.50

please refer to this topic:
http://www.tipidpc.com/viewtopic.php?tid=194171

i already inserted a formula in crystal report. like this:

Sum({Employee.amount})

but i get an error. saying "a number of field or currency amount field is required here"

any ideas? :(

[__avd]

Datatype of amount field must be numeric. For text fields use string (text) to numeric conversion functions.