Scan Reorder in a User Defined Way

HI, I want to scan-chain reordering after placement (or in placedesign) in a manner given below Suppose I have two scan-chains 1 and 2 Chain 1 (3 flops) - a, b, c chain2 (3 flops) - d e f What I need is to re-stitch chains in a given order (defined by user ) for example in this case chain 1is now a, b,d and chain 2 consists of c e f. Due to some issues I want to restitch chains in a definite order, a typical scan-order does is only placement aware and reduces wire length, However, in my case wire length is not an issue and I want a user defined scan-chain stitching after placement. Pls note that grouping the scan-cell so that they are kept together while re-ordering will not work here as, scan-chain that we are getting from front-end dft flow (in scan def) is different from the user defined chains that we want post placement. Thanks Kumar