Try the LPAD() function: https://www.ibm.com/support/knowledgecenter/en/SSEP7J_8.4.0/com.ibm.swg.im.cognos.fnct_ds.8.4.0.doc/fnct_ds_id5734LPad.html
The examples in that documentation are helpful. Hope this helps!
The examples in that documentation are helpful. Hope this helps!