Can any one help me in vba code?

I need to increase the loop value automatically till lost regards in
the work sheet, but I don't how to write the code for that

Example , now I am manually increasing the loop value whenever loop
reaches the records

A= "prakash"

For I = 1 to 300
If Sheet2.cells(I,1)= A then
Sheet3.cells(I,3)= sheet2.cells(I,2)
End if
Next I

See the above example if the sheet2. Column1 less then 300 records
then, there is no problem in loop execution, but if the sheet2.
Column1 exceed more than 300 records, then, I cant get my datas, I
should manually increase I (loop) value 500, again the sheet2.
column1 exceed more then 500, I should increase I(loop) value
again, instead of this, is there any code for automatically increase
or execute till the last records, whenever regards increase, loop
also execute till the last record,

I hope you all understand my request, If any one help me it will be
very useful for me