To specify a special register for a parameter value

From the SP Test tool, click a stored procedure on the tree view.
On the Parms tab, right-click the Value column corresponding to the parameter whose value you want to edit, then click Insert special register.
From the drop-down menu that appears, click the special register you want to use to store the parameter value.
Click Insert special register again to paste the reference into the Value column.

Note:

The special register specification appears in the Value column in the following format:
<SR=specialregistername>

Do not manually modify the SR= portion of this specification. Doing so can cause the stored procedure to execute improperly.

However, you can modify the specialregistername portion of the specification by typing over it. For example, if you selected the CURRENT DATE special register, you could modify it to be CURRENT DATE - 100 DAYS which is then used instead of CURRENT DATE. Be advised that modified special registers cannot be validated.
Numeric parameter values must be valid for the stored procedure to execute properly.
For input parameters, you can also specify a value by entering it directly into the Value column, using the Edit Entry Values editor, or by specifying a side file.
You cannot specify a special register to store an output parameter value unless you have set the Allow Output Side Files option to True.