For everybody who did not know, here is the solution.
mcToolGetDataExDbl()
mcToolGetDataExInt()
mcToolGetDataExStr()
local dblVal, rc = mc.mcToolGetDataExDbl(number mInst, number toolnum, string fieldName)
local strlVal, rc = mc.mcToolGetDataExStr(number mInst, number toolnum, string fieldName)
You can find this and many more undocumented functions it in the autocomplete list in the LUA Editor.
Thanks to Brett from the Tech support staff for his help.
An example i did is attached.