User is forced to Approve

Hi All,

I am an ABAPer I have designed a workflow with 7 stages of approval with Buttons below(user Decision) 

1)"APPROVE"    Button

2)"REJECT"       Button and

3)"NEED CONFORMATION" Button .

Tested and successfully working. Nowin 3rd and 4th stage of approval User must "APPROVE" he should not "REJECT"   nor  "NEED CONFORMATION .

1)Redesign with single approval is not agreed.

2)can we disable other two buttons(REJECT and NEED CONFORMATION) for only 3rd and 4th stage with any function modules.

3)Any function which will do this.

Thanks Hari