Can we change the data type of a field based on the value of the field

HI Gurus,

My Requirement is as below -- Could you please guide me

in the Printable Adobe form -- for ex - as usual for dates fields in the Object Pallette the object type is a date/time field  and for quantity/currency fields corresponding fields are taken

now in case the either the date, quantity or currency is initial in place of displaying 0.00 or empty date we need to display N/A (Not Applicable)

for this I would like to change the data type of the field

to put it simply --

we need to change the data type of date field from DATE&TIME to Char type to hold N/A or  Quantity field to Char field to hold N/A

how can we realize this in SAP adobe forms

Thanks in Advace

Ramchander Rao.K