>How can I set readonly property to false for a particular row on a grid which is readonly?

Smitha,

If you want to change ReadOnly status depending on field value (say, if myNumber>100 you want ReadOnly=.f., otherwise .t.) you can put in Grid Init:
this.ColumnMyNumber.Readonly=(myNumber<=100)

And you probably should Refresh your grid in AfterRowColChange (for me it doesn't work without refreshing).