"End Date" should update depending on the "Reason" selected

Hi Experts,

On Lead Screen, I have REASON picklist.

Component/View : BT108H_LEA / Detail

Context Node/ Attribute : BTSUBJECT / STRUCT.CONC_KEY

If i select the REASON = "For 3 Months" / "For 6 Months", a warning/error message should appear that remind to update the Lead "End Date" to update the same. (i.e. if End Date had been 12/31/08 and a warning/error message would be displayed to "Change/maintain the Lead End Date." to 3 months / 6 months)

Else.

If the Reason is picked as "For 3 Months" the "End Date" should change to current date + 3 months.

(i.e. if current End Date is 12/31/08 then it should change to 03/31/09.)

"End Date" component details.

Component/View: BT108H_LEA/Detail

Context Node/ Attribute : BTLEADEND/DATE

Can you please help me in achieving the same.

Cheers

Mythili S